Ground Probing Radar techniques can be used to analyse projects at shallow depths of investigation. At the University of Aveiro, Portugal, GPR techniques have been widely used in Archaeology, Geotechnics, Hydrogeology and Environmental problems. However, these techniques should be always used in conjunction with other geophysical methods so that a better overall interpretation is proposed.
Archaeological application of GPR in conjunction with seismic refraction and electrical resistivity measures from Infante Square, Porto (North Portugal) are discussed. GPR was used to delineate bedrock topography as well as local diffraction from buried structures. GPR interpretation is supported by seismic refraction interpreted using the Generalised Reciprocal Method. The overall geophysical model was tested and adjusted using local mechanical soundings. The information was integrated using a GIS for geophysical and geological interpretation and for further utilisation by archaeologists and architects.
The value of magnetic susceptibility as a tool for the location of archaeological sites has been demonstrated on many occasions. However, recent studies have shown that magnetic susceptibility also has the potential to aid the identification and interpretation of deposits during excavation.
This paper examines the information that can be provided by in situ measurements of magnetic susceptibility on archaeological deposits such as hearths, cultivated soils, middens and industrial residues. The discussion is illustrated by case study examples using deposits encountered during the excavation of a multiperiod settlement mound at Scatness, Shetland. Significant variations in magnetic susceptibility were found in both excavated deposits and exposed sections, allowing distinctions to be made between features resulting from different anthropogenic activities, including heating, cultivation, domestic residue disposal and iron smithing. It also appeared possible to detect changes in the use of fuel sources over time. The relative merits of the Exploranium GS meter and the Bartington field coil for studies of this nature are presented and in situ magnetic susceptibility measurements are compared with laboratory measurements of the same contexts. In addition, mineral magnetic measurements, soil micromorphology, soil chemical analysis and archaeological evidence from artefact and ecofact assemblages, are used to confirm the interpretation of the deposits examined. It is demonstrated that in situ measurements of magnetic susceptibility can provide the archaeologist with a rapid, simple and cheap measurement, which can be used during excavation to indicate the origin of deposits and any subsequent anthropogenic modification.
Magnetic (M hereafter) and electromagnetic (EM hereafter) methods are two different but complementary ways to study soil magnetic properties which intervene in pedogenis and anthropogenic processes by measuring respectively any types of magnetisation and magnetic susceptibility (in frequency domain).
Recent studies established a linear relation in Fourier domain between M and EM data. This method allows to deduce induced magnetisation from EM data by using linear filter. The Fourier transform of the induced magnetisation is obtained by the direct product of the Fourier transform of magnetic susceptibility by the ratio of the Fourier transform of the impulse M response on the Fourier transform of the impulse EM response generated by a magnetic dipole. The tests realised on synthetic data allowed to prove the efficiency of this filter and to evaluate the influence of the different parameters. It has been established that the depth of the dipole has a very limited influence on the filter and can be approximated by a single magnetic dipole.
The linear filter has been thus tested on field data from different archaeological sites: a pottery workshop from Iron Age (Verdun sur le Doubs, France) and a metallurgic workshop from medieval period (Melles, France). The results show a good correlation between filtered EM data and magnetic data. The result will essentially depend of the estimation of the depth of the magnetic source. The filter must thus be tested with a single dipole at different depth to be sure to obtain the best result.
For three years, the archaeological site of Apamée upon Euphrat was investigated by electric and magnetic methods in relation with the excavations and the topographic study. These geophysical surveys have greatly contributed to the global understanding of this site, which will disappear in December 1999 by the formation of a lake due to the building of a dam. This mission of rescue organised on this Hellenistic City required fast and efficient methods. Thanks to a greater and greater efficiency and the edition of maps more and more detailed, the geophysical methods are confirmed today very adapted to this context. The use of the Cesium gradiometer (G-858, Geometrics) for the magnetic method allowed maps of a rare quality revealing the urban system (streets, walls of defence, stocks of habitations). They constitute a real archaeological document, which permitted one to make a pertinent choice of the locations of the excavations. These excavations have completed the geophysical information, studying sectors in an out of the way place with the magnetic method, but localised in the urban scheme from the geophysical maps. Twelve hectares have been surveyed among the thirty-five hectares of the site. Different sectors occupied by thick orchards can't be prospected with the Cesium gradiometer but they should be razed before the filling in of the lake. We hope thus to complete the map of Apamée before its disappearance under the waters.
Over two archaeological sites, magnetic prospections were carried out with gradiometer equipment. For each site, several geophysical responses corresponding to different historical time scales are superimposed. The need for a diachronic interpretation arises to separate the different structures and replace them into the proper time window. This can be achieved by the confrontation with all available historical sources and archaeological features.
The archaeological site of Ribemont-sur-Ancre (Somme) has an extension of 70 hectors. Studied for 30 years, this major site known as a reference for Celtic civilisation, is nowadays reinterpreted as a Celtic trophy from the second half of the IIId century B.C., superposed with a pre-augustean sanctuary. Since its discovery in 1960, a lot of missions of aerial prospecting (Agache 1960, 1964, 1970, 1978) and archaeological excavations have taken place. If the spatial distribution of remains is well known - a large temple, a worship enclosure, baths, a theatre and insulae-, many questions are still unsolved :
However, magnetic prospection has enabled the detection of new structures: Celtic ditches, a craftwork area, etc. Confrontation of magnetic data to old field boundaries and vertical aerial photographs taken by the Royal Air Force during the first world war allows us to interpret the origin of the different anomalies in terms of historical periods over 2000 years.
The archaeological site of Authumes (Saône et Loire) is located on a mound over the Doubs valley. Surface findings span over an area of approximately 700 x 300m. They extend from the 3rd c B.C. until 4th c. A.D. Concentrations of artefacts from one period seem to be well concentrated over different areas. However, no marks appears on the available aerial photographs. In order to gain information in a very short time to convince political authorities, the magnetic prospection was required: a surface of 3 ha was surveyed within two days. The map shows a palimpsest of superimposed structures probably associated with the different states of occupation of this site. Further excavations and geophysical surveys should confirm the time superposition of the discordant structures and the possible relationships between them.
South-east Scotland, an area some 80 km by 80 km in extent, is characterised by its low rounded hills up to 600 m in height, heather-covered on the higher slopes, cut by narrow valleys, and bounded on the north by the broad estuary of the Firth of Forth and a wide coastal plain, on the east by the North Sea, on the west by higher hills of similar form, while to the south the border with England is formed, in part, by the River Tweed, but, for the most part, by hedges and stone walls in farm land, cultivated similarly on both sides of the line. The Royal Commission on the Ancient and Historical Monuments of Scotland has been carrying out consistent aerial reconnaissance in south-east Scotland for over twenty years. While the presence of pitted features had been recorded in earlier years in antiquarian accounts, as well as by aerial and field survey, it was in 1978 that an association was noted between pit-alignments and settlements appearing in cropmark and earthwork form and attributed conventionally to the Iron Age.
There are two main forms of linear boundary in the cropmark record, linear ditches and pit- alignments or interrupted ditches. They are paralleled as upstanding monuments by linear earthworks, which usually appear as a bank and a slight, presumably quarry, ditch and, in a very few examples, as a series of small, regular depressions, accompanied by a low bank, which match the pit-alignments. The pits are usually quite small, between 2 m and 3 m in diameter and often poorly defined. Pit-alignment is a convenient morphological term, which may be applied to monuments of different periods and cultures. Examination of the distribution patterns in GIS show a clear concentration in south-east Scotland, and in certain areas within it.
With the 1990s came a survey break-through, allowing the relationship between pit- alignments and linear cropmarks to be clearly established, and, with the advent of GIS in the Royal Commission, came the ability to view these very small individual features both in isolation and as part of larger grouping, which can, in the most extreme example, be seen to run for at least eight km. The digitised transcription and rectification of pit-alignments, linear cropmarks, the settlements with which they may be associated and earlier monuments, which may have had significance in the laying out of boundaries, and the incorporation of information into the GIS is time-consuming work, of which perhaps 20 % has been completed. Examples were recorded running uphill into the currently uncultivated moorland and even to the cliff edge above the North Sea, implying a completeness of control of the land, that required detailed physical boundaries defining small areas, which might be compared in scale to the modern field pattern, the product of enclosure between the late seventeenth century and the early nineteenth century. The results of a series of recent pollen analyses across southern Scotland and northern England would suggest that from about 350 cal. BC, there was not a very considerable expansion in the intensity with which agriculture was practised across the area, and this dating would not conflict with field survey. The evidence for an ordered and complex system of land division in south-east Scotland is considerable, and necessarily raises questions about the social organisation of the inhabitants of the area before the advent of the Romans.
An extensive fluxgate gradiometer survey was undertaken on a large housing development at Northampton, England. The results, based on a 1.0 x 0.5 sample density, were unambiguous, with evidence for clear settlement foci. However, it was felt that some of the detail, especially for individual dwellings was missing. A research design was formulated to see if the missing elements could be located. In particular the strategy was aimed at establishing the differences, if any, between two magnetic instruments (fluxgate gradiometer and caesium vapour gradiometer) of different sensitivity on 'typical' British soils and to establish what variation an increased sample density achieves.
Firstly, two enclosures and a 'ring' ditch were re-surveyed using the Geoscan FM 36 and data collected on a 0.5 x 0.125 m grid. The area was then surveyed using a Scintrex Smartmag SM-4G on the same nominal sample intensity. The results were analysed to highlight:
This study benefits from two further factors. Firstly, a 'blank' area was surveyed to analyse soil noise in an effort to understand true levels of identifiable anomalies. Secondly, all areas were then stripped and archaeologically excavated. As a result, direct comparison has been made between the instruments and the physical reality of the buried evidence and not simply a qualitative 'analysis' between greyscales. This work has far reaching implications about how we go about survey, both in terms of strategy and instrumentation.
We present the results of a new 3D tomographic multimethodological procedure using a probability function, which allows to infer the presence of anomalous sources in an optimum way without a priori constrains. In particular, we use Self Potential and Geoelectrical data, showing that the 3D tomographic reconstruction of sources, generated by both a natural electric field and an artificial one, can improve the information about the prospected targets. As a matter of fact, the 3D Self Potential tomography aims at defining the charge distribution across electric discontinuities and the 3D Geoelectric tomography aims at contouring the volumetric distribution of the resistivity. Therefore, the two tomographic procedures complement each other giving a more complete and reliable interpretation. We discuss the results from the study of the state of preservation of the Axum Stele (Rome, Italy). The 3 D tomographic procedure allowed us to identify missing materials, microfaults and linking bronze dowels implanted inside the Stele between the overlaid blocks.
The investigation of mining archaeological sites in the Alps requires a special approach to investigation due to the difficulties of the terrain conditions (topography, vegetation). Using a gold mining region from the 15th and 16th century in the Gasteinertal (High Tauern) as a testbed, a method of prospection was developed and tested which is being called the integrative model of prospection. The main characteristic is a partition of the process into a number of phases, thus achieving a significant degree of improvement of the cost-result ratio. Through the specific use of research, non-invasive and invasive methods, the prospected area is being successively reduced from phase to phase by a ratio of about 1000:100:10:1, while the density of information increases at the same time. The area of prospection is indicated by research (phase 1). The location of finds is determined by systematic archaeological and geomagnetic profiling (phase 2). In phase 3 the boundaries of the site areas are determined through geophysical methods (geomagnetics and electromagnetics). Finally in phase 4 the detailed scenario of the site is investigated through the use of archaeological, geodetic, geophysical and geochemical methods and the area to be dug is determined. During the excavation, geophysical methods are used for detailed investigation of difficult digging areas, archaeologically not accessible areas (steep inclines, rock fall areas, snow fields) and for the resolution of problems of the geology of the deposit (SP method) and of mining technical problems. Also petrophysical methods (rock density, susceptibility) are being used as well, both in situ and on finds (ores, slags, soil discolorations).
In the area of the mining field Bockharttal and the precious metal smelter Angertal mining, processing and smelting installations were prospected and archaeologically excavated in the years 1994 to 1998. The method of prospection, its significance for planning and execution of the excavation and the archaeological results for this application will be presented.
This paper is intended to show the advantages of new techniques as Remote Sensing, Global Positioning Systems and Geographic Information Systems on the design of research projects directed towards the aims of Landscape Archaeology. Centred on an area of contact among a variety of geographical environments, this project tries to recognise and understand the differences on settlement patterns on a diachronic perspective, employing the new technical implements and generating databases linked with archaeological prospection.
The chosen area is organized along the corridor defined by the river Guadiana Menor, establishing a link between the coastal ports of south-eastern Spain with the important mining area of the upper Guadalquivir. The first stage of the analysis of settlement patterns should be guided to the detection of archaeological sites, as well as to determine the physical characteristics of the environment. Apart from other indispensable tasks, as the revision of the previous archaeological and historical information, there are two essential topics to be accomplished: archaeological prospection and the stock of any relevant geographic information. With this aim, we can benefit of new tools, as Remote Sensing Analysis (RSA), Global Positioning System (GPS) and Geographic Informations Systems (GIS). All of them involve a considerable advance on the capacity of analysis of any research regionally oriented. However, the novelty of these techniques in their archaeological application, and the specific character of each topic and of this particular area, compel us to generate concrete methodological instruments in order to adapt those resources to the research, during fieldwork and on the laboratory analysis. In this paper, we will try to present how the integration of the three systems leads to obtaining meaningful advantages in the attainment of the research objectives.
From a technical point of view, the combination of RSA and GPS allows us to connect directly observations made during fieldwork within the information system. The result is what we could "archaeological prospection satellite-assisted". From the point of view of theory, a central premise is the systematic integration of the archaeological aims of fieldwork, basically the location and documentation of archaeological sites on a regional area with those specifically geographic in character, within a single system of information, planning and evaluation. Conventional programs of archaeological prospection at a regional level are scarcely efficient in relation with these approaches. This ineffectiveness comes usually from the application of criteria that are exclusively archaeological on the selection of survey areas, sampling patterns and prospection models. This implies in many cases a remarkable difficulty to establish generalizations from -by example- data about site distribution, and, in any case, a deficient assignment of economic resources. The introduction of geographic criteria proves to be essential in this context Within this methodology, the documentation system includes the conventional archaeological information as an element of landscape, different enough to require specific criteria of classification, but in any case, articulated with other factors and variables of geographic or biological character.
The value of wetlands lies in their extraordinary potential for the preservation of archaeological remains. This value has been reflected by the number of projects which have been centred around finding and assessing sites within wetland landscapes. Despite this, however, there has been very little development in the methods of prospection which have centred around fieldwalking and ditch surveys. This paper outlines a new method of prospection within wetland landscapes using GIS to model three dimensional surfaces from high resolution, high accuracy surveys of micro-topography. This method has been able to identify the locations and nature of buried archaeological deposits due to differential shrinkage of biogenic deposits relative to clastic sediments which is reflected in the surface.
Two sites were surveyed using high accuracy differential Global Positioning System (GPS) equipment at a standard deviation of 0.02 m. They were surveyed in transects aligned upon ranging rods at a surface resolution of between approximately 8.0 m and < 1.0 m in areas of greater archaeological potential. The data from these surveys was processed using ARC/INFO© Geographical Information System (GIS) software to generate an interpolated cell-based surface. This surface was generalised in a number of ways including basic contour banding and light-source allocation to provide hill- shading in order to highlight natural and archaeological features represented through elevation, aspect and slope. The results from this modelling were later assessed through ground-truthing.
The first site was at Sutton Common (South Yorkshire) in the Humber wetlands. Here a pair of Iron Age lowland enclosures exist within a wetland landscape, positioned on 'islands' on opposing sides of an infilled palaeochannel. Enclosure B remains as an upstanding earthwork monument while enclosure A was bulldozed in 1980 and was under intensive arable agriculture until 1997. Despite seventeen years of ploughing, the outline of enclosure A was clearly visible along with a number of further features such as the presence of a ditch on its western side. Also the position of a causeway between the enclosures, crossing the palaeochannel, was indicated.
Ground-truthing at this site was assisted through a programme of excavations, commissioned by English Heritage, which were positioned on the basis of the model. This work revealed a direct correlation between features identified from the modelling and those identified in the excavation trenches.
The second site was Meare Village East (Somerset) in the Somerset Levels. Here an Iron Age site had been identified on a raised peat mound within a peat-filled hollow. The settlement was characterised by clay spreads and mounds which were occupied by industrial remains and hearths. The results from the GIS model of this site reflected the positions of many of the known clay mounds which cover the site as very slight rises, most of which were imperceptible on the ground. Further it identified a number of other mounds which had been located through a magnetometry survey. Other mounds were indicated outside of the known area of the site. The results were checked by excavating a number of borehole transects. These identified correlations with some of these new mounds, but also a lack of correlation with others which appear to have been influenced by later activity.
In each of these cases the identification of archaeological features has been possible due to the increased shrinkage of biogenic sediments relative to clastic sediments within the framework of the current drainage regimes at each site. At Sutton Common, this increased shrinkage was identified in the peat-filled palaeochannel and the archaeological ditches. At Meare Village East, the scenario was reversed with the increased shrinkage lying in those areas not covered by the clay mounds. Overall the method has proven to identify archaeological features within wetland landscapes which cannot otherwise be seen on the ground.
The site of Tell el Farkha is located immediately to the north of the modern village of Ghazala (14 km east of Simbillawein), in the Sharqiya province, Eastern Nile Delta, Egypt. The site was identified by the Italian Archaeological Mission (led by R.Fattovich) in 1987, the excavations were carried out between 1987 and 1990. From 1998, the excavation have been continued by the Polish Archaeological Mission, led by M.Chlodnicki (as a joint project of the Poznan Prehistoric Society, the Jagiellonian University and the Polish Centre of Mediterranean Archaeology in Cairo).
The site is located on the top of a sand gezira and extends over an area of c. 400 x 110 m., with a maximum height of about 4.5 m over the level of the cultivated plain. It is marked by three mounds along the northern edge of gezira and a gentle slope delimited by the village houses in the south (fig. 1). The maximum thickness of an anthropogenic deposit, above the water table, can be evaluated at 5-6 m.
So far, the excavations have shown three main occupational phases of the site, the earliest one going back to the Predynastic period (4th millennium B.C.), and the later ones to the Late Predynastic/Early Dynastic period and the Old Kingdom (3rd millennium B.C). The last two occupational phases are characterized by occurrence of mudbrick buildings. The Predynastic phase exhibits only pits and light clay installations.
Most of the site is covered with a thick mantle of halfa grass, and a powdery earth stratum build up by collapsed mudbricks and aeolic redeposition. This stratum contained appreciable amounts of pottery, flints and stones. Below this deposit (10-40 cm below the surface) some fire installations, pits and first evidence of architectural remains occurs. In deeper layers many rectangular and semicircular constructions made of mudbrick were found, some of them paved with mudbrick floor. Total area of excavation before 1990 was 192 sq.m. In 1998-99 the excavated area was 282 sq.m. large.
In 1998, a geophysical test was carried out in the western part of the site, in the area of 4,000 sq.m. The survey revealed distinctive settlement traces. In 1999, the whole site was surveyed, i.e. the area of 27,000 sq.m. A number of obstacles were caused by the fact that the survey was carried out in the area exploited by a densely inhabited village (huge amount of metal objects on the surface, traffic, driving of cattle etc.).
The fluxgate gradiometer FM36 (by Geoscan Research) was used. The test survey was in the grid of 0.5 x 0.5 m., the final survey in the grid of 0.25 x 0.5 m. Apparent traces of buildings from the latest settlement phases - the ones closest to the surface (Early Dynastic/Old Kingdom) are well visible on the magnetic map (fig. 2). The traces were registered on the middle mound (between Y=100 and 240) and the eastern mound (Y above 240, outside the area presented on the map enclosed). The survey revealed the general disposition of buildings. Traces of the buildings start disappearing towards the north; it results from the increasing thickness of the deposits covering the remains of the settlement. The survey shows that the settlement stretches southwards below the
contemporary houses. The survey has already been primarily verified by excavations, e.g. a distinctive, negative linear NW-SE anomaly (between Y=170 and 180, X=40 and 60) turned out to correspond to a mudbrick wall, located immediately under the surface (fig.3); the wall was accompanied by concentration of ashes (a positive anomaly at the NE side of the wall).
The nature of a number of rectangular anomalies (between X=90 and 120, Y=30 and 50) on the eastern mound is not clear. They may correspond to a cemetery (?); but that will be clarified during the next campaign.
Bibliography:
M.Chlodnicki, R.Fattovich, S.Salvatori, Italian excavation in the Nile Delta: fresh data and new hypotheses on the 4th millennium cultural development of Egyptian prehistory, in: Rivista di Archeologia, XV, 1991, p.5-33.
M.Chlodnicki, K.Cialowicz, Tell el Farkha (Ghazala), Excavations 1998, Polish Archaeology in the Mediterranean 10, Warsaw 1999 (in press).
About 100 Vertical Electrical Soundings (VES-Points) were measured at the site of Tel- Halawi, located on the left side of the Euphrates just before flowing into the Assad Lake in northern Syria. The VES-Stations, of only 2 m spacing, were distributed along 9 profiles (5 meters apart from each other), covering the southern part of the site (s. maps in Fig-1-). The electrode array, adopted for doing geoelectrical survey, was a modified Schlumberger configuration (pole-dipole array with the B-electrode placed far enough to be of negligible effect), which was suitable to be run with the following steps: OA = 1; 1.5; 2; 3; 4; 5; 7; 10 m, while the separation of potential electrodes (MN = 0.5 m) was constant all over the soundings.
The resistivity data measured in the field were then treated and plotted as resistivity cross sections of different pseudo-depths, showing the specific influence of the different targets laying at the corresponding depths. The procedure, even though more time consuming, looks as a very promising technique for discovering near-surface targets through resistivity survey, reflecting successively the resistivity variations with depth, and separating anomalies in regard to their depth situation below the surface within the first ten meters. It offers also higher reliability of results, due to confirmed response of the subsurface targets noticed as multiple anomaly on several cross sections with gradually growing depths. Many of these anomalies measured along the resistivity profiles were verified through excavation work.
Chusonji is the Buddhist temple constructed in the 12th century at Hiraizumi city, Northeast Japan. In this temple three mummies are still preserved: they are
All of them were Fujiwara chieftains. In the coffins of these mummies many silk materials were used.
The amino acid composition may be determined from 13C NMR (Nuclear Magnetic Resonance) for these silk materials. Due to the degumming of the materials they are not solved into any solvent. Only solid state NMR can be applicable. Solid state one is insufficient in the resolution compared with solution one. In Figure 1 are shown typical spectra. Chemical shift splittings are observed in C=0 region between Gly and Ala. The mole fraction of these two amino acids are different with each other.
Possible candidate of the origin of such difference in the fraction is climate (especially temperature) when silkworm was reared. Actually, from the comparison with dendrochronological data good correlation was obtained. However, the number of samples is confined to only three. In order to overcome the insufficiency of number of the samples we have to introduce an alternative strategy. It is NMR observation of modern silk reared in definite temperatures. In this case we can use solution state NMR to silk gland extracted from silkworms. Chemical splittings were observed in C ? region due to good resolution and the mole fraction was able to determine for Gly, Ala, Ser and Val. Three species were used as follows:
Temperature dependence was clearly observed for all species. Qualitative coincidence can be confirmed between the fraction of above and this NMR data. Only the numerical values for Habataki cover those for silks in the coffins. From the comparison between them temperature was estimated as follows:
According to the document (established in the 14th century) of the sutra stock house of Chusonji, in the central, the left and the right coffins Kiyohira (the first), Motohira (second) and Hidehira (third) were preserved, respectively. This document is thought to be reliable. However, there is still one unsolved problem: there are two ways on the definition between left and right. In Japan the definition was usually done from the respected person side. The respected person means Buddha image in this case. This is completely opposite definition from that of prayers side. From the NMR investigation in this study the definition from the respected person side is supported. The definition has to go back to the former one at least from this study. This conclusion is reasonable from the standpoint of Japanese traditional definition between left and right.
Magnetometer surveys continue to be used over a wide range of archaeological sites throughout the UK and have met with a high degree of success given the generally favourable geological and soil conditions found throughout the country (Clark 1990). The majority of these surveys have been conducted with fluxgate gradiometers which offer the advantage of both affordability and rapid data acquisition in the field, constrained only by a modest sensitivity compared to high resolution caesium vapour sensors. Whilst primarily designed for aeromagnetic applications the suitability of optically pumped magentometers for archaeological survey has long been recognised (Ralph 1964) deterred only by the cost of the equipment and difficulties with field operation. To this end, German and Austrian geophysicists have extensively developed caesium instrumentation for archaeological applications which currently allow high resolution magnetic data to be collected at a similar rate to fluxgate surveys (Becker 1994?).
Despite the obvious advantage of higher sensitivity that caesium magnetometers provide relatively few surveys have been conducted with caesium magnetometers in the UK compared to the continent. This is due, perhaps, to both the historical development of fluxgate instrumentation in the UK (Alldred 1964) and the abundance of magnetically enhanced soils found throughout the majority of the country (Dearing et al 1997). Numerous geophysical surveys, supported by subsequent excavation, attest to the suitability of fluxgate instruments to a provide a more than adequate sensitivity over the resultant well magnetised archaeological features that these sites produce. However, the scarcity of direct comparisons with caesium data has limited the assessment of high resolution magnetic survey and the benefits this may offer over conventional fluxgate gradiometers.
The aim of this study is to present results from a series of comparative surveys conducted over a range of sites in England through an ongoing collaboration between the Bayerisches Landesamt für Denkmalpflege, München and the Archaeometry Branch, Ancient Monuments Laboratory, English Heritage. A range of monument types and geological substrates have been investigated encompassing sites both favourable to magnetic survey and those where fluxgate gradiometers have met with difficulty discerning weakly magnetic anomalies. The study includes comparative magnetic data sets collected with a pair of adapted Scintrex CS2 caesium vapour total field sensors and Geoscan FM36 fluxgate gradiometers at similar sample intervals (0.25m x 0.5m). For further comparison, additional fluxgate data was collected at more typical reconnaissance sample intervals (0.25m x 1.0m) and also with a reduced sensor height, closer to the operational height of the CS2 sensors, to maximise the response from weakly magnetised features.
Figure 1 illustrates the results the comparative survey of the Stonehenge Avenue, Wiltshire, where both fluxgate and caesium instruments have detected the course of the two parallel flanking ditches and a scatter of pit-type anomalies. It is of interest to note discrepancies arising in the interpretation derived from the two magnetometer plots which, no doubt, reflect a combination of instrument sensitivity and differing levels of confidence applied by the two research groups during the analysis of the data. This issue is explored further at sites where excavation following the geophysical survey has allowed a direct comparison between significant magnetic anomalies and the underlying causative features.
Results are also presented from a similar comparison between fluxgate instruments and the commercially available Scintrex SmartMag 4 caesium vapour gradiometer conducted over the site of a suspected timber temple revealed within the Stanton Drew stone circle, W England
(Figure 2). Whilst the SmartMag has a much lower sensitivity than bespoke systems derived from aeromagnetic caesium sensors it has the advantage of greater availability and increased sensitivity over fluxgate gradiometers.
Thanks to a seven-year lasting cooperation between France and Hungary, I had the opportunity to fly approximately 80 hours over Hungary. These aerial prospections were mainly directed by Mr. Ren Goguey, who is a pilot as well as aerial archaeologist, of the Aerial Archaeology in Burgundy, France. The material is now archived in the Laboratory for Rauminformatik at the Archaeological Institute in Budapest, which was established because of emergency diggings on the highway M3. The collection includes not only images from René Goguey, but also from us and several foreign scientists as well as old copies from other Hungarian institutions.
We recognized in the beginning that the possibilies of aerial archaeological photography do differ very much depending on the geographical and agricultural situation nowadays. Hungary has very many habitats for aerial photography, especially at landscapes which were not affected too much by agriculture. The images can be interpreted not only from an archaeological point of view, but also from a standpoint of Holocene geology. While flying above Hungary, one gets a very good impression not only of the landscape but also of the landscapeīs transformation. The results are alarming. Changes which are obvious from 80 hours in the air are strengthened by the impression we get while comparing aerial images from this time.The documents prove, that aerial habitats vanish and more important, a dramatic transformation of the landscape takes place. We have to take leave not only from the habitants but the whole landscape.
More than 29 archaeological site are found in the area of the lake of Chalain (Jura) in France. The stratigraphy from these sites span from the 32nd to the 24th century B.C.. Two settlements have grown during Neolithic times between the west and the east shore of the lake. The first one has shown a stratigraphy between the Horgen culture (32nd century B.C.) and the Chalain culture (-24th c. B.C.). To the east, the second one, was investigated mainly by augering. The geophysical survey took place on this side with a Pulse Ekko 1000 radar.
The stratigraphy of the sites is made principally of dark organic matter deposits within a white lacustrine chalk. In order to study these deposits, the archaeologist can either make ordinary digging, necessarily limited to a small area, or use auger-borings but with a dense sampling strategy. In the latter case, he will have to face the problem of interpolation between the borings.
Despite the fact that GPR was used for other archaeological sites, the case of Chalain is specific : i) the vertical extent of some of the deposits is very thin (a few centimetres at a depth of two meters or more) and makes this kind of target a challenge for a geophysicist ; ii) due to water level changes during historical time, some of the deposits are partly under the present level of the lake or in the transition zone.
Three GPR profiles were done along the shore and six perpendicularly to the shore. Information is available down to a depth of 3.4m. Reflectors show clear patterns such as on-lap and off-lines figures. Several strong reflectors with a North -East dip are also visible and one specially at a depth of 3.2m. Horizontal reflectors are due to ringing. Six auger-borings were performed along one profile and have shown the presence of reduction material (charcoal) and also organic matter . In particular, three levels named as H, K and O can be correlated from one drilling to the other. They can be associated with settlements from the late Neolithic .
The superposition between the stratigraphic log obtained from drillings and the radar reflectors has enabled a good correlation between them. In particular, the oldest level named O (Horgen culture) corresponds to the strongest and the deepest radar reflector. This demonstrates that it is possible to detect and map the O strata and the more recent levels without destruction. Moreover, a trial radargram was done above the lake level and proved the feasibility of a non-destructive detection of archaeological layers under 6 meters. In summary, this case study shows that, with a sufficient low frequency antenna, it is possible to detect anthropic levels within chalk deposits in a lake and to precise their depth and lateral extension. It would be then possible by making a high resolution GPR survey with a dense sampling scheme, to map the extension in three dimension of the archaeological deposits since 6000 years without destruction.
The archaeological site "Furna a do Estrago", situated in the municipality of Brejo da Madre de Deus, Pernambuco State, represents an important parameter in the reconstitution of the prehistoric landscape in the semi-arid environment of Northeast Brazil during last the 11.000 years BP.
Based on the systematic study of this site, analysing the cut 7A of the "Furna do Estrago" - constituted of seven archaeological layers -, a reasonable contexture of past occupations resident in the Furna was possible, evidenced respectively between 11.060+-90 BP (layer seven); 9.150+-90 (layer six); 8.495+-70 BP (layer five) and 1.040+-50 years BP (layer two).
Starting from general ideas about the Quaternary, situating the "Furna do Estrago" in this period, specific methodologies have been applied that come for other areas of the scientific knowledge (grain-size analyses, morphoscopy and X-ray diffraction), palinology, zoo and the phytoarchaeology graphic resources met in informatics, for the space reconstitution of the site and areas of bigger human activity in the resulting archaeological layers.
The ordination of the related aspects in the analysed stratigraphic section, differentiated well by the resultant layers, with a depth reaching 1,40 m in an area of 7m2, allowed a direct correlation between the expressive amount of identified archaeological records, associating them with the responsible sedimentary dynamics for the formative process of the stratigraphic profile.
In this relation it was observed, from the grain-size analysis, homogeneous sedimentary process in the stratigraphic sequence between the milleniums, where the degree of selection and the proper grain-size are characterized by a small difference between the layers, with the predominance of an average sandy material in a sedimentary regime of low energy.
Such assertion, associated to the mineralogical results (X-ray diffraction), especially represented for the clay minerals: kaolinite and illite; and to the zoo and phytoarchaeological aspects, allowed to indicate for the datings mentioned above, a warm period with high temperature in the Pleistocene/Holocene limit (11.060+-90 years BP), following by a warm and dry period for 9.150+-90 years BP, again a dry period at 8.495+-90 years BP, suffering later a climatic mild, probably between 6500 and 4.000 years BP (layer four - without dating, but with intense zooarchaeological and palynological indicators characterizing humid periods - probably the "Optimum Climatic One"), reaching contemporary climatic trends to the semi-arid of Northeast Brazil, only near 1.040+-50 years BP.
The zoo and phytoarchaeological characterizations confirm the sedimentological and mineralogical perspectives for the prehistoric environment in the Furna, by the expressive or scarce features in confrontation with the already argued parameters.
From the botanical point of view, all identified species with characters of typical Caatinga plants, have their bigger concentrations in the form of archaeological material dispersed among the layers.
From the faunistic point of view, the expressive presence of the categories Mammalia, Reptilia, Amphibia and Molusca, predominantly between layers 5, 4 and 3, permit to infer that the best phase of adaptability to the environment, for the past groups, is given between 8.495+-70 BP and 2.000 years BP, attributing for the previous periods not so favourable environmental conditions, responsible for the scarcity of the food resources.
This information, coherently organized in the stratigraphic section and reconstituted by operation of computer science, made possible the indivudualization of strategic considerations about the prehistoric occupations, classifying, from the distribution of the archaeological records in the profile, the areas of bigger anthropic activities and availability of the resources.
At last, as presented in this work, a sequence of the environmental periods which would have crossed the prehistoric groups of the Agreste of Pernambuco, characterizing the landscape of the last 11.000 years BP and indicating the most favourable periods for the development of the occupations situated in this time span are shown.
The Middle Neolithic circular ditch at Schletz is located in the hilly landscape of northeastern part of Lower Austria and was detected by aerial archaeology in 1981. The interpretation of the aerial photographs was done using analytical photogrammetry. For the whole procedure, an analytical plotter device with a PC 386 was used. This device has a high precision in measuring picture coordinates (at about two mycrons) and therefore produces highly accurate 3D maps of the relevant archaeological information. In that way, the outline of the circular ditch could be drawn which was used later on for setting out the grid used by the geophysical prospection. Additionally, a raster of 3D-points and 3D-breaklines were measured and consequently, the digital terrain model of this site was calculated.
In 1995, a magnetic survey of the site using a high resolution Caesiumgradiometer was carried out. An area of two hectares was measured in a raster of 0.5 x 0.25 m. The data were visualised as digital images and georeferenced for interpretation. The archaeological interpretation shows a highly eroded single circular ditch with two interruptions, which were used as entrances. Each entrance feature is flanked by two short ditches, which meet the main ditch at a right angle. Using GIS, all the different prospection data were digitally combined to create additional images for subsequent archaeological interpretation.
To derive 3D reconstructions of the archaeological features a magnetic model was constructed. This was done by 3D modelling of the subsurface using dipole spheres of equal size and homogenous susceptibilities. A primary distribution of the spheres in the 3D space was produced and the anomaly was calculated. The calculated image was then compared to the measured data and changed until the measured data were accounted for within a minimum error by simulated annealing. In Schletz, the susceptibilities of the ditch fill could be measured during the excavation in 1995, when a trench was laid out through the V-shaped ditch. During the stratigraphic excavation, each layer of the ditch-filling was registered by a tachymeter and magnetically analysed, which lead to a precise understanding of their size and magnetic influence. The consequence of these results for the 3D modelling were an improvement of the magnetic model of the filled ditch which lead to more accurate reconstruction results. The result of the 3D magnetic modelling was intersected with the digital terrain model and in that way visualized within its landscape. Aerial photographs were then mapped on the terrain, which can then be looked at from any direction and animated to produce virtual flights. Other details, as the single posts of the palisade could be taken from the 2-yeras excavation. The postholes were digitised and thus, the whole palisade could be reconstructed.
Images as magnetograms, digital aerial photographs, reconstructions of the ancient environments or photographs from excavated parts of the monuments can hierarchically be mapped on the digital terrain model. Integration of reconstructed archaeological features based on additional excavation data produces a virtual model of monuments that had been covered by soil over thousands of years, bringing them back to (virtual) life.
The Roman town Teurnia is located in the area of the "Holzerberg" in todays St. Peter im Holz (Carinthia), covering approximately 17 hectares. Since 1845, excavations have been going on, which revealed parts of the towns wall, the forum, residential terraces and several early christian churches. Among them also the episcopal church dating from the 5th and 6th century A.D on top of the Holzerberg. A part of the town at the eastern bottom of the Holzerberg was photographed several times from the air by S. Tichy, a member of Carinthiaīs building surveyorīs office between 1978 and 1992. These oblique photographs show the crop-marked town map of an area of 23.000m2. To be able to integrate the information of these photographs into a complete town map, the aerial archive at the institut for Prehistory in Vienna was consulted.
The area of interest expands over several narrow fields with different crops, each responding differently to the underlying archaeology. This results in a patchwork, where photographs show cropmarks only in single fields. Fortunately, since the photographs were taken over several years, cropmarks could be recorded on each field. Therefore, all of the photographs had to be used for interpretation. Additionally a vertical stereopair (1:10.000) was available, produced by the Austrian air force during summer 1980. It covers the whole area of Teurnia. The oblique photographs were taken using a non-calibrated small format camera with unknown focal length. Unfortunately, some photographs showed a bad distribution of possible control points.
To be able to deal with these problems, we decided to use a bundle adjustment, where control points (= points with ground control) and tie points (= points visible in two or more photographs, but without ground control) are measured on all photographs and all measurements are adjusted to the ground control values in a single solution. The whole procedure was done digitally using the software SoftplotterTM on a Silicon Graphics O2 workstation with 256MB RAM. The vertical photographs and the slides were scanned with 2000 DPI. Ground control was measured using a total station. After the orientation, topographical data (3D-points and breaklines) were measured and a digital terrain model calculated. Consequently, this was used to rectify all of the photographs which were oriented by the bundle adjustment. The resulting orthophotographs have a pixelsize of 0.2 m. The accuracy depends on the quality of the distribution of the control points and lies between 0.5 m in the central part (which contains most of the archaeology) and up to 3 m in the more distant parts.
The interpretation was done using the geographic information system ERDAS ImagineŠ. Using the provided image enhancment techniques, the orthophotographs were treated with contrast stretch, Wallis filter or crispening. All of the georeferenced orthophotographs and their filtered variations were interpreted on screen. The interpretation drawing was combined with digitized results from the previous excavations which had been done between 1971 and 1978. The combined analysis of the results from the excavation and from aerial interpretation provided archaeologists with new clues to the extent of the settlement area during the 1st to 3rd century A.D. It will also function as basis for future archaeological activities as geophysical prospection.
The use of thermal infrared imaging for archaeological prospection has received relatively little attention compared with other geophysical techniques. However, it appears have potential for identifying archaeology under permanent pasture which is a land use that covers an extensive part of the UK rural landscape and which rarely yields crop marks in conventional vertical or oblique photography. An experiment was carried out to test the ability of airborne thermal imagery to detect shallow ground disturbance at the site of the Battle of Bosworth (1484) in Leicestershire, UK. The relatively uniform temperature of the ground surface normally hides information contained in day-time thermal imagery. Instead, we invert the heat flow equation using pre- dawn and mid-day image pairs acquired from an airborne thermal line- scanner to compute a measure of diurnal heat capacity (apparent thermal inertia). In theory, we would expect structures that lie buried beneath the ground to have a diurnal heat capacity distinctive from the surrounding soil.
First, we present a methodology for deriving diurnal heat capacity (apparent thermal inertia) from airborne thermal imagery. Secondly, we interpret the raw and processed imagery for the presence of buried structures and shallow ground disturbance. Finally, we assess some of the interpreted structures by comparing their location and morphology with independently acquired, ground based, magnetic and resistivity surveys.
Bosworth battlefield in Leicestershire provides an excellent test site partly because there is controversy over its precise location and disturbed ground features may help to reconstruct the geography of the battle. Also, there is known to be a deserted medieval village lying unexcavated within the study area. The modern landscape around Bosworth differs markedly in appearance from that of the fifteenth century. Straight hedges have enclosed the former open fields and the marshlands, known to have existed, have been drained and improved. Today the land around Bosworth is predominantly under permanent pasture and does not yield good crop mark evidence from traditional vertical or oblique photography.
Ulucak Höyük archaeological site is located 10 km. away from Izmir. The artificial hill includes different settlements from Early Bronze Age to Late Roman Period. In this area, the archaeological excavation has been carried out since 1995. This excavation showed that the Ulucak archaeological site is very important for the history of Izmir city and environs in Early Bronze Age and later on. The geophysical surveys have continued to map all artificial hills by different geophysical exploration techniques such as magnetic, resistivity, self potential and EM-VLF since 1998. The magnetic gradiometer studies were carried out by Geoscan FM- 36 fluxgate gradiometer in 3900 square meter area, approximately. In this study, the measurement intervals were chosen as 0.5m on the profiles approximately 1m apart. Furthermore, the data were collected in 39 area by 10m x 10m. In the processing, the data were firstly united in an appropriate co-ordinate system for all survey areas. Then, the arranged data were processed with different signal processing techniques and the enhancement map of the magnetic survey was obtained (Fig.1). Gradiometer measurements show that magnetic anomalies are generally condensed in the southern and eastern part of the artificial hill. Moreover, the magnetic anomalies are directed in two different directions. First anomaly group is N-S and E-W, and seem to similar the Late Roman foundations found by the archaeological excavations in the southern part of Höyük. The second anomaly group was near the Early Bronze age settlements in the eastern part of Höyük.
Resistivity studies have been carried out by twin array with 0.5m x 1m grid interval in the Höyük. The aim of this study is to measure all this area by the resistivity method by the end of 1999. The preliminary results are quite interesting and the buried archaeological settlements were clearly defined in resistivity maps which are similar to each other. Especially, the resistivity and magnetic are in accordance in the southern part of the Höyük. In addition, the self-potential method was applied in the some anomalous area which high magnetic and resistivity values were obtained. The data were collected by two different measurement arrays, gradient and total area systems. As can be seen from the gradient map, the self- potential anomalies are low in amplitude. However, it is directed to N-S and E-W direction as magnetic and resistivity maps are (Fig.2). This result is important to support the usefulness of self-potential methods in archaeological prospection. Furthermore, a new correction technique was tested to develop the self-potential method. The data showed that the new correction technique is very useful in archaeological prospection, and data quality was rather increased compares to the classical correction techniques in self-potential method.
In addition to these geophysical surveys, the EM-VLF method was used along some test profiles and areas. The results were interesting and previously identified anomalies observed clearly in magnetic, resistivity and self-potential maps, were again obtained.
The most efficient method for investigating circular ditch systems from the Middle Neolithic (Lengyel culture) situated in homogenous loess is high resolution magnetic prospection. Their shape, the number of ditches and entrances and the state of preservation become obvious. By using caesiumgradiometers in a raster of 0.5 x 0.25 m even the remains of inner wooden palisades become visible in the magnetogram. This high resolution and high precision data forms an excellent input for 3D magnetic modelling to reconstruct the depth, width and shape of the ditches.
The reconstruction of the ditches of such a large monument is achieved by simulating the measured data using a simplified magnetic subsurface model of the filled ditches. The subsurface model is realised by single dipole sources with specific magnetisation arranged in a 3D array. The distribution of the dipole sources is determined by an iterative optimisation algorithm similar to simulated annealing. This iterative algorithm has to minimise two measures: the absolute difference between the measured data and the modelled magnetic anomalies and a regularisation term to produce a smooth ditch interface, which may include pre-information about the ditch section. The specially developed optimisation algorithm is called leaped annealing and is able to optimise various magnetic models. The reconstruction problem is therefore converted into an optimisation problem with plenty of parameters. For the monument Steinabrunn 184.800 parameters have to be determined.
The particular magnetic model was developed based on archaeological-geophysical excavation results and uses two independent magnetic horizons to represent the complicate stratification of the fill of the ditch. The first horizon models the upper parts of the filled ditch, which show high magnetic susceptibility contrast. The other models the lower parts of the ditch with lower magnetic susceptibility contrast. The application of the developed model is able to successfully reconstruct all parts of the monument due to its ability to adapt to different fill and varying state of preservation. The magnetic modeling of Steinabrunn uses an array of dipole sources with 0.25 x 0.25 m spatial and 0.1 m depth resolution.
The fully automatic reconstruction takes a few hours on an up to date computer and is divided into the following steps. In a preprocessing step the corrected data are classified to eliminate strong anomalies of modern source from the reconstruction. Then a first reconstruction is computed using an regularisation term which smoothes the ditch interface. The result of that first reconstruction is used to detect the shape of the ditches. This information is necessary to be able to integrate the known shape of the ditch section into the regularisation term within the final reconstruction step. The mean difference between the measured and the modelled magnetic anomalies of the rondel Steinabrunn is 0.085 nT ? 0.53 nT, the ditches have a reconstructed depth up to 3.2 m. The reconstructed ditch can be intersected with the digital terrain model and mapped with additional information and reconstructed features from excavation results, like the palisade. New sights of such a Middle Neolithic monument can be achieved by animation of the scene to help understanding the purpose of these oldest Middle European monuments.
The utility of GPR in the study of subterranean chamber graves was tested in an experimental program combining prospection and other forms of non-destructive investigation with limited excavation at a sixth-century cemetery site in southern Kyushu.
The existence of subterranean chamber graves at the Himori Site in Takaharu Village, Miyazaki Prefecture, was first revealed when part of a natural knoll was levelled for agricultural purposes in 1969. Investigations of the tombs, conducted from that time on by the Board of Education of Miyazaki Prefecture, show the basic shape of these features to consist of a vertical shaft no more than 2 m deep, from which a narrow horizontal passageway and burial chamber 2 m x 2 m or smaller are tunnelled in one direction only (Fig. 1). The entrance to the passageway was typically sealed with a pile of stone slabs, preserving the chamber as a hollow cavity, while the shafts had been filled in completely. The Prefecture also conducted a shallow excavation over a 440 m2 area at the top of the knoll in 1981, locating ten pits, rectangular in horizontal plan, believed to represent the upper portions of vertical shafts corresponding to an identical number of chambers.
In September 1997, GPR was conducted over the area of the Prefecture's investigation at the knoll's crest. Anomalies suggesting the presence of chambers were readily detected in profile (Fig. 2), and horizontal time-slice analysis (developed by D. Goodman) showed these correlated closely with the shafts previously located by the Prefecture, presumably indicating the directions in which the chambers lie (Fig. 3). As no such anomaly was seen in association with Feature 8, however, it was provisionally concluded from the GPR results that the identification of this feature through conventional excavation as a grave shaft was mistaken.
The conclusions derived from the GPR survey were subsequently tested through limited excavation in December 1998. Feature 8 was sectioned east-west, with the southern half excavated, showing it to be a shallow pit ending shortly below the modern surface, and not leading to a chamber. Similar sectioning of Feature 3 (Figs. 1, 4) confirmed the existence of a passageway entrance on the northeast side of the shaft, as suggested by the time-slice images. Careful examination of the section showed that the chamber had been reopened after its initial construction, presumably for the purpose of a subsequent burial, and that the entrance had been sealed with a thick wooden board, rather than stone slabs (Fig. 1). Observations such as the latter are beyond the current capabilities of research by prospection alone.
Finally, a hole was opened through the dirt filling the entrance to the chamber of Feature 3, and first a miniature video camera, then a digital still camera were inserted, both attached to the ends of long poles, to obtain visual images of the chamber's interior. The digital camera in particular provided useful images showing the skeletal remains of two or more individuals, at least one of whom was an adult female, which had been arranged after decomposition of the flesh along the back wall of the chamber.
A new high capacity railway line, the so-called Koralmbahn, is planned to connect the cities of Graz and Klagenfurt in Southeastern Austria. In the East of the Koralm range, which will be passed by a long tunnel, it runs through the Laßnitz Valley, where numerous archaeological sites from the Neolithic to the Roman periods were expected, but only a part was known.
For the evaluation of possible impacts to the archaeological heritage existing data were not suitable, so a systematic archaeological survey was carried out to cover the whole valley floor completely for a length of ca. 20 km. Different methods were applied in combination to check reliability of observations and to facilitate interpretation. In addition to the ground survey, aerial prospection was carried out. The detailed mapping of morphology made it possible to detect some regularities in site distribution and to define important parameters for the positioning of settlements. As the valley is still flooded today, the deposition of alluvial sediments and the possible occurrence of sites below younger sediments had to be investigated by a number of boreholes at selected cross profiles.
The project was carried out, including preparatory work, fieldwork, interpretation of data, generating of digital maps and preparation of the final report within six months from March to August 1997. The archaeological digital data (Arc/Info files) were introduced to the Styrian land information system (GIS Steiermark) to be used for other planning purposes also.
The 41 unquestionable sites belong to 47 findspots of nearly all periods from the Aeneolithic to the Modern Periods, 38% of them are Roman. 86 areas were defined as possible archaeological zones (Fundhoffnungsgebiete). Due to the low density of prehistoric or Roman finds or ambiguous evidence; here more detailed prospection measures must be applied to interpret the occurrence of finds.
As an unexpected result it could be shown that Roman sites situated even on the lowest part of the valley floor are not covered by alluvial sediments, indicating that floods did not affect them. A complete Roman landscape with villae rusticae and settlements or single buildings of different types was investigated. The distances between them are 1.5 to 2.2 km for the large ones and several cases 0.5 to 0.7 km only. Parts of the Roman road, levelled burial mounds and settlement sites were observed by aerial prospection as well.
All sites detected were graded according to their cultural and scientific significance providing basic data for decision making in the planning process. It has to be stressed that the sites were already known in the earliest stage of planning. This provides the key to introduce archaeological sites like other environmental data with the goal to minimise impacts, so the chance for the preservation of important sites is improved considerably. Measures for the further stages of the project, which are necessary from the archaeological point of view, were proposed as a guideline. For example, intensified prospection including geophysics, soil probing, the archaeological involvement during the construction works and excavations, where necessary.
The excellent cooperation between the planning authority (Eisenbahn-Hochleistungsstrecken AG, Projektleitung Koralmbahn), the Sites and Monuments Office (Bundesdenkmalamt), the direction of public works of the Styrian Government and the firm carrying out the archaeological prospection and evaluation (ARGIS) may be considered as a model for future large scale construction works in Austria.
A three day time constraint, minimal information on the expected archaeology, even less details about the site conditions and a director with three camera crews and a script demanding instant results. These are the challenging conditions faced by archaeological geophysicists working on the popular Channel 4 Time Team series in the UK. Yet experience gained in the day-to-day world of archaeological evaluation work in Britain is ideal training for such a challenge.
Nearly 60 programmes have been made, viewing figures are regularly over 3 million people and the series has been sold worldwide to the Discovery Channel. Using results from the first seven series, including those not transmitted, this paper will demonstrate how the problems and constraints are overcome. Discussion will also consider the two transmissions that have been broadcast "live" over holiday weekends. The ethics of "simplifying" often very complex science will be considered, as will the problem of making geophysics exciting without being professionally challenged. The integrity of the programme will be contrasted with experiences on other archaeological television programmes.
The Hindwell Neolithic enclosure was discovered from aerial photographs taken in 1994. Some further parts were found in 1995 and 1996 so that some 75% of the perimeter is now known. Excavations in 1995 and 1996 revealed the site to have dated to 2700 BC (late Neolithic) and to have been delimited by a wooden palisade of posts some 8m long and weighing 4 tonnes. Approximately 1400 posts had been used and the enclosure covered 34ha.
Little was known of the interior of the site as it was covered with pasture fields. Caesium-vapour magnetomery was undertaken over these 'blank' areas to try and identify internal features and/or areas of activity, the position and nature of the entrance and whether or not the line of the enclosure could be detected beneath a Roman fort which overlies the eastern perimeter.
Prior to the Geophysical survey a full physical survey was undertaken at the site to try and detect microcontours and to place the site into real space. Geophysical survey was undertaken over the same grid. The results indicated that the enclosure appears to have been empty or else the internal features were of such an ephemeral nature that subsequent agriculture has removed all traces. Some large pits were located, however, as well as some interesting anomalies on the perimeter. The survey of the Roman fort produced important information regarding the phasing and internal arrangements of the monument and detected the palisade running below the fort. This also, unexpectedly, survived as a slight earthwork in this area.
The project was funded by the European Commission, The Cambrian Archaeological Association, Cadw: Welsh Historic Monuments, The Discovery Programme and The City Archaeology Service, Zwolle.
Classical archaeomagnetic investigations based on laboratory analysis of oriented samples are under discussion now (Abrahamsen,1986). The focus of discussion is shape magnetic anisotropy effect. The shape anisotropy causes magnetisation vectors refraction of homogeneous object. Archaeomagnetic refraction is mainly formed by TRM vectors. Refraction of TRM probably causes the significant error of archaeomagnetic investigation results. Development of methods for refraction error correction is actual (Abrahamsen, Koppelt, Voss 1997).
Evaluation of archaeomagnetic errors due to the refraction was done on mathematical model of a pottery kiln. The kiln was found during magnetic prospecting done in Crimea (Ukraine) in 1988. Magnetic structure of the kiln was has been worked out on base of algorithm which includes two parts. At the first part the object magnetic structure, determined by the TRM vectors is modelling. This magnetic structure is formed by ancient geomagnetic field when temperature of the object is near to blocking temperature (Radhakrishnamurty, Likhite 1969). At the second part final magnetic structure of the object due to by modern geomagnetic condition is calculated. Calculations were done by computer programme „DEGMAG" (Ermokhine, Glazounov 1989). Mathematical modelling results allow to conclude that the scattering of the TRM vector directions of kilns is connected not only with well known reasons but also with demagnetisation effect of these objects. That conclusion has practical interest as allows to contribute corrections to the procedure of the archaeomagnetic research. The places of selection of the oriented samples of kilns should be chosen taking into account the results of the object magnetic structure modelling. Additional investigations of the model show that vector of total magnetic moment of the object is practically parallel to ancient geomagnetic field vector. This fact is reasonable to use for archaeomagnetic object dating at the condition of shape magnetic anisotropy. Methods of the magnetic moment vector determination are well known in theory of inverse magnetic problems. Algorithms based on methods of approximation and spectral analysis for the inverse problems solution were done. For the algorithms realisation information about geometry of the object, distribution of magnetic susceptibility and factor Q of kiln has to be known. This information is available after archaeological excavations of kiln. Example of practical test of the spectral method for medieval isometric pottery kiln dating is presented (Glazounov, 1985).
Recent developments in 3-D high-resolution multi-image processing and contouring as opposite to destructive testing have greatly contributed to improve the quality of geophysical information in archaeological reconnaissance surveying. Ground Penetrating Radar (GPR) offers very high-resolution sounding capability with detection of features of the order of a few tens of millimetres thickness at ranges of several metres.
In this work, the results of high-resolution GPR surveys carried out in two archaeological sites characterised by different geological environmental conditions are presented. The two archaeological sites are: Roman Villa - Cazzanello (Tarquinia, Viterbo - Italy), and Forum Novum - Vescovio (Stimigliano, Rieti - Italy). The Ground Penetrating Radar profiles were carried out using an SIR System 10 A+ (GSSI), equipped with different antennas, operating at 300 and 500 MHz. For the first site, GPR profiles were collected in an area with dimensions 140 m x 60 m; in the second site two different area with dimensions 60 m x 80 m and 40 m x 80 m were investigated. In all areas the interval between adjacent profiles was 0.5 m. To enhance the interpretation of the GPR data, radar signal processing and time-slice representation are worked out. The results obtained on shallowly buried structures indicate that the floor plans of the buildings can be clearly identified from time slice analysis.
The objective of the geophysical survey of the Early Iron Age site of Ndondondwane (ca. 750 AD) was to identify potential subsurface features in order to target areas with high probability for excavation. The problem with the use of most geophysical surveying techniques on EIA sites in southern Africa is the lack of comparative studies. Also, few sites have yielded the kind of high ceramic concentrations, burnt clay floors and other features that would be easily identifiable by most geophysical instruments. Most structures in such sites are of an ephemeral nature - unburnt dung floors and thatch roofs. As a result, a Geonics EM38 conductivity instrument was used in the survey. It measured differences in soil moisture which allowed identification of even relatively ephemeral structures on the site. The results of the survey and implications for its use on other sites will be discussed.
In the year 1998 in the area of the Roman town Flavia Solva, Province Noricum (Styria, Austria), a primary resistivity survey was carried out during field practice with students in archaeology in two days. Target of this prospection campaign was the localisation of the municipium's forum which has been searched for in vain for over 125 years. The towns rectangular street system, known from partial excavation and aerial evidence, is also known from a series of Claudian (41-54 AD) towns in the Northern provinces (Trier, Cologne, Avenches, Virunum). Common to all of them is a predominant main street which implies the importance of the surrounding buildings (insulae). Due to considerations on the towns map known so far the area of Insulae XXIII and XXVI has been identified as a possible location of the forum.
To verify this hypothesis we carried out a resistivity survey using two RM15 resistivity meters with multiplexers MPX15 (Twin Array) covering 7000 m² on parcels owned by the Federal Authorities. The street system is evident on the digital image representation of the resistivity data measured with 0.5 m electrode separation in 0.5 x 0.5 m raster and with 1 m electrode separation in 0.5 x 1.0 m raster. The georeferenced images of the 0.5 m, 1.0 m and a „pseudogradient" constructed by division of the two data sets were archaeologically interpreted using the GIS ArcView. Parts of the Insulae XXIII, XXVI and XXX were covered by the survey which confirmed the main features of the existing town map.
The archaeological interpretation of the resistivity survey testify a multi phase building activity for the Insula XXIII. The western part of this insula seems to be free of buildings. In the North along street L equally big rectangular rooms seem to follow the street, reminding of horrea or tabernae. South of these rooms four nearly equally big rectangular house complexes seem to be adjacent, built over in antiquity in the West. The recognisable apses and the compact building modus as well as the big free place oriented to the North-South directing main street could point to a more monumental building.
The neighbouring Insula XXVI with a width of approximately 60 m belongs to the largest building complexes of Flavia Solva. The length of approx. 75 m, typically for this insula, derives from the reconstruction of the excavation results in Insula XXX and V.
The prospection testifies an obvious division of the examined area in a western part mainly closed by buildings and a less closed eastern part. There is a clear structure of the buildings in a middle room which is divided in two parts, resembling a hall accompanied by smaller rooms. Adjacent in the East is a big free place surrounded by two parallel halls. The exterior hall seems to encircle the whole building complex. The inner hall terminates a place whose eastern part is build over by the Federal Highway. The interpretation of the buildings of this insula is still difficult at present. The big free place surrounded by halls could be interpreted as the forum of Flavia Solva searched for a long time. Also the buildings in the southwestern part of the insula may be easily compared to the prospected findings of the civil town of Carnuntum in 1996 which were interpreted as the forum. The solution of the evolved archaeological questions to locate the forum of Flavia Solva will only be verified by surveying the area east of the Federal Highway. For higher resolution and to include depth information a radar survey also covering the fields east of the Highway is planned for 1999.
Although lead was a major source of economic wealth in antiquity, there have been few studies of lead smelting sites in Britain. This study presents a geophysical characterisation of Medieval lead smelting sites (bales) in Swaledale. Sites were surveyed using aerial photography, fluxgate gradiometer surveys, earth resistance surveys, TM808 metal detector surveys and both volume and mass specific magnetic susceptibility surveys. The surveys demonstrated that sites were characterised by an area of magnetic noise, usually situated uphill from an area of bare ground, with scatters of lead slag on the surface. The results showed that bale sites appear to have consisted of several small areas of burning, often with associated fuel stores. While some of the bales were stone lined, some consisted of a small burnt area. The results suggest that the difference between bale and blackwork oven is less clear than was previously thought.
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Hesse A., Renimel S., 1978, "Reconnaissance des limites du site néolithique de Khirokitia (Chypre) d'après les distributions superficielles de vestiges et la résistivité du sol", Revue d'Archéométrie 2, 5-18.
Hesse A., Bossuet G., Rémy J., Renimel S., Tabbagh A., 1978, "Succès de l'archéologie prospective à Saint Romain en Gal", Archéologia 122, 7-17.
Hesse A., 1980, "La prospection des vestiges préhistoriques en milieu proche-oriental: une douzaine d'années d'expériences géophysiques", Paléorient 6, 45-64.
Hesse A., 1982, "Une nouvelle hypothèse de tracé pour un rempart de la ville", Argos, Bull. Corresp. Hellénique, CVI, II-Chroniques et rapports, 10-15.
Hesse A., Doger E., 1993, "Atelier d'amphores rhodiennes et constructions en pierre à Hisarönü (Turquie): un cas original de prospection électromagnétique", Revue d'Archéométrie 17, 5-10.
Hesse A., 1994, "La prospection archéologique: des mesures extensives sur deux dimensions de l'espace", Histoire et Mesure, n° thém. IX-3/4, 213-230.
Hesse A., 1997, "De l'intérêt raisonné des investigations sur plusieurs paramètres en prospection archéologique", Colloque Geofcan, Géophysique des sols et des formations superficielles, 11-12 sept. 1997, Bondy, France, 111-115.
Hesse A., 1999, "Multi-parametric survey for archaeology: how and why, or how and why not?", Journal of Applied Geophysics, Proceedings of the 1st International workshop "Electric, magnetic and electro-magnetic methods applied to cultural heritage", EMEMACH 97, sept.29 - oct.1,Ostuni, Italie, vol. 41, n° 2-3 , march, 157-168.
Hesse A., Andrieux P., Atya M., Benech C., Camerlynck C., Dabas M., Féchant C., Jolivet A., Kuntz C., Mechler P., Panissod C., Pastor L., Tabbagh A. et J., in press, "L'Heptastade d'Alexandrie (Egypte)", in Empereur J.Y. "Alexandrina n°?", IFAO Le Caire, 45p env.
To demonstrate the potential of archaeological prospection data, computer aided reconstruction is used to illustrate the archaeological interpretation of a part of the Roman civil town Carnuntum east of Vienna. This part is mainly known from data collected during the last three years by an integrated prospection approach combining aerial archaeology, geomagnetics, resistivity mapping and GPR. By combining archaeological knowledge with architectural construction techniques from the Roman period we try to derive virtual reality scenes that can be shown to a wider audience to illustrate a reconstructed scenario of archaeological sites not yet excavated. By using software for architectural modelling as well as desktop virtual reality techniques we create virtual walkthroughs of the Roman civil town of Carnuntum/Austria.
The computer aided reconstruction has been performed with modern architectural software as well as some general purpose modelling tools that are especially suited to generate complex forms like in the Roman period. Furthermore existing three-dimensional libraries of Roman architectural art helped to create realistic virtual scenes inside the computer. To manage the data complexity of a realistic visualisation for a part of an entire town several methods for data reduction and data abstraction have been used to produce visual appealing results, although the amount of data had to be reduced drastically. The computer based reconstruction is a combination of three-dimensional architectural models as well as plausible definition of materials from the roman time. The base for the reconstructed buildings have been derived from the evaluated geophysical prospection by archaeological interpretation carried out by archaeologists. The height of the buildings have been estimated with archaeological aid from the prospected floor plan and the measured wall thickness. The shapes of the buildings have been reconstructed using the floor plan again and additional knowledge from already excavated buildings at the same site.
The archaeological reconstruction visualises a large area of about 8 ha. The virtual walkthrough starts from outside the town from the necropolis situated aside the main road leading into town from the south. By passing the town wall with the fortification ditch in front we enter the town still on the main road. We pass several houses (shops, housing areas, workshops), a temple and enter a large public building at the southern end of the forum. After crossing the forum the walk leads through a basilica to a monumental public bath.
The computer aided reconstruction is a fast and cost effective way to present the archaeological interpretation model derived from prospection data to a wider audience. Computer aided reconstruction of archaeological sites provides a wide base for discussion in archaeology still giving the chance of dynamic development of the scene which is a major advantage compared to conventional reconstruction.
Situated in the hinterland of the Phoenician-Roman city of Ossonoba, the modern Faro, with its important port on the Atlantic coast, the Roman villa of Milreu is one of the best preserved ancient monuments in Portugal. In 1877, Estácio da Veiga excavated large areas of these ruins, such as an extensive peristyle with rich coloured fish-mosaics, bath-buildings and a late Roman sanctuary (nymphaeum ?). From the 19070s to the mid-nineties, the German Archaeological Institute in Lisbon concentrated its investigations on the sanctuary. In March 1999 a new phase of the evaluation of the ancient site was initiated and, with the support of the IMPULS foundation of the VDMA (Frankfurt am Main) and the Friedrich-Schiller-University at Jena, it was possible for the first time to carry out a resistivity survey of a Roman rural monument in the Algarve.
A Martin-Clark five-probe and a Geoscan RM4 meter were used to allow the site to be prospected at different depths. The aim of the survey was to explore the possibility of further buildings in this already extensively excavated villa complex. In all, five areas of the site were surveyed:
Area 1 (fig. 2) was a 30 x 28 m grid to check for constructions lining the road which leads west from the entrance to the villa towards the river, Rio Seco. Earlier excavations immediately to the north had provided evidence of structures on a different alignment from the villa and presumably of an earlier date. The area towards the western end of the site, was very badly obscured by the spoil heaps from past excavations and no unambiguous archaeology was detected. There were, however, a number of very localised high spots in the north-east quarter of the grid, and although these might only represent natural boulders, they could also be interpreted as post pads or stone-choked post holes. Faint traces of linear structures on a similar alignment to the excavated structures could also be identified.
Area 2 was a 35 x 25 m grid situated behind the still well preserved late Roman sanctuary. The ground was partly impeded by dumped material as well as modern rubbish deposits which tended to mask any archaeology in the area. Nevertheless, the survey did reveal a slightly curved band of high readings leading off to the south-west behind the villa proper which has tentatively been identified as a path or road.
Area 3 (fig. 3, 30 x 23 m) lay in an orange grove to the east of the visible ruins. The trees were planted in rows, each of which was served by an irrigation system, and the survey results reflect this by displaying heavy banding. This can, however, be at least partly filtered out making it possible to identify underlying structures, some of which might represent remains shown in the antiquarian plan of Estácio da Veiga. There is, for example, a series of square shapes towards the southern end of the grid that may form an extension of the barrack-like buildings already known closer to the sanctuary (pars rustica). To the north of these there appear to be two more rectangular structures that do not appear on the old plan and which raise the possibility that more buildings may exist than has been assumed hitherto.
Area 4 lay just to the east of a sixteenth-century farmstead and was designed to see if the Roman period walls found under this building could be traced outside it. There was only room for an 8 m wide (x 30 m long) grid between the building and the site's boundary fence but, despite its small scale, the survey proved successful in identifying structures connecting a mosaic-paved room under the farmstead and an atrium with a fountain to the south.
Area 5 lay just inside the modern entrance to the site, between grids 1 and 2. It consisted of very dry, compacted earth topped by a thin layer of pea gravel. No new structures were detected, but the survey was able to pinpoint structures that had been excavated previously but then backfilled.
In summary, although the presence of significant deposits of excavation spoil had meant that no great faith had been put in the ability of resistivity survey to produce useful data at Milreu, good results were obtained which have contributed to our understanding of this remarkable Roman site. The present work was merely a test survey and it is planned to carry out more extensive prospection in the coming year.
Bibliography:
F. Teichner, Die römischen Villen von Milreu (Algarve / Portugal). Ein Beitrag zur Romanisierung der südlichen Provinz Lusitania. Madr. Mitt. 38, 1997, 71-98.
During the 1998-season spent in the Oder mouth area, the National Museums team has completed a lengthy seismic survey of all three channels through which the Oder discharges its waters into the Baltic Sea. . The instrumentation used was a combination of high-tech and general acoustic devices which permitted the registration of bottom and sub-bottom anomalies. Few of these targets were inspected by divers afterwards, but the experience gained in this kind of environment enables a better understanding of the application of Chirp-type sub-bottom profiler to underwater archaeological prospection, and in general to the application of seismic prospection to underwater targets. The present knowledge of geophysical prospection in underwater environments is increasing. The focus favours clearly geological applications, while archaeological applications are still in the incipient phase of experimentation. The material presented here tries to increase the understanding and interpretation of bottom and sub-bottom anomalies in the light of the experience gained in the field.
The need to cover large areas of coastal zones for the broader understanding of active geomorphological processes has led to some experiments with aerial photography in the Roskilde fjord. Part of the „Wendish Seafaring" project which deals with the reconstruction of past landscapes in the Oder mouth area, and the experiments carried out over the Roskilde fjord area were directed toward optimisation of flying ceiling, selection of film type, photographic technique and camera type, and finding the best flying daylight time. The results were processed in the facilities offered by both institutions in Roskilde and they are presented here in the light gained by the authors during the flights. The results permitted the observation of several new features regarding the geomorphology of the area, and they constituted the basis for a renewed effort in dealing with deltaic formations and morphodynamics in the coastal zone.
Pulse GPR (Ground Penetrating Radar) has been widely used in the field of archaeological prospecting recently; however, we have often encountered the limit of its applicability. So, the authors have developed another type ground penetrating radar, a FM-CW (Frequency- Modulated Continuous Wave) radar (Kamei et al. 1996). In the FM-CW radar, the transmitter frequency increases or decreases linearly with time. As the frequency cannot be continuously changed in one direction in practice, the transmitter frequency is triangularly modulated between 100MHz and 500MHz. The period of the triangle waveform is 50msec. If there is a reflecting object at a distance R, the echo signal will return after a time T=2R/v (where v is a velocity of electromagnetic wave in soil). If this echo signal is heterodyned with the transmitted signal, a beat signal will be produced. This beat frequency fb is proportional to the delay time T; fb = aT, where „a" is a rate of change of the transmitter frequency and a=16Hz/nsec in this case. Because the FM-CW radar is on the basis of detecting frequencies, the vertical axis of FM-CW radar profile becomes a frequency axis; furthermore, higher S/N-ratio is expected than pulse radar. And the FM-CW radar image is not affected so much by the „ringing", because the transmitted signal whose frequency spectrum is limited inside the bandwidth of antenna. Signal processing techniques play an important role in detecting frequencies from the beat signal and in making images in the FM-CW radar. In this paper, such techniques are discussed.
As a pre-processing, a technique of emphasizing higher frequencies is introduced. In a pulse GPR, a time-varying gain (STC) is applied in order to compensate for propagation loss, but this technique is not applicable to a continuous-wave GPR. In the FM-CW GPR, a signal from a deeper target appears in higher frequency domain. It is well known that differentiating a time-varying signal results in emphasizing the higher frequency part of its power spectrum at the slope of 6dB/oct. By differentiating a beat signal of the FM-CW GPR, deeply buried targets appears more clearly in the GPR image.
Many spectral-estimation methods such as FFT, MEM (Maximum Entropy Method), filter bank, etc., are applicable for detecting the beat frequencies. They have both advantages and limitations, respectively; so, a proper method should be chosen for the purpose, multiple methods may be also available.
In this FM-CW GPR, the transmitter frequency changes from 100MHz to 500MHz in a half period of the modulating triangular waveform. By setting the length of the time window for spectrum analysis shorter than a half of the modulation period, we can select the frequency band used for imaging; the higher frequency, the shorter wavelength, then the higher resolving power, physically.
A delay time T is detected as a peak at a frequency of fb (=aT) in the power(amplitude) spectrum of the beat signal in the FM-CW radar; furthermore, the delay time T also appears in the phase term of the spectrum. So, we can make another image using phase spectra. In a phase spectrum by FFT, a step-like change of phase appears at a frequency corresponding to the delay time T. Since there are some cases where detection of step-like change is easier and/or more accurate than peak detection, a FFT phase spectrum image of the FM-CW GPR is available.
Bibliography
Kamei, H. et al. (1996):"A 100-500MHz Band FM-CW Ground Penetrating Radar for Archaeological Prospecting.", Abstracts of Archaeometry 96, Urbana, USA, May 20-24,p.57
A total area of about 300 hectares within the modern communities of Petronell and Bad Deutsch Altenburg can be classified as an archaeological area, which only partly has been archaeologically explored up to now. A complete inventory of all available aerial photographs will soon be compiled. A new general view of known archaeological structures may now be obtained by using photogrammetry for the interpretation of aerial photographs.
So far parts of the area have been successfully prospected applying geomagnetic and/or geoelectrical methods and GPR. Both aerial photography and existing geophysical data indicate that the archaeological heritage has suffered severe damage by deep ploughing. As constant excavation and reconstruction work is done at the "Archäologischer Park Carnuntum", rescue excavations have to be initiated quite often because of modern construction projects. Those excavations tend to become long term projects. Scientific interests frequently are in conflict with the economic and housing development of the today's villages Petronell and Bad Deutsch Altenburg which are situated right in the archaeological zone. Thus establishing an appropriate prospection strategy applying non-intrusive methods for Carnuntum, the largest archaeological landscape in Austria, seems to be an important step towards further archaeological research and monument protection as well as regional planning.
The presented case studies may be regarded as prime examples of combined archaeological- geophysical prospection. The available aerial photographs are complemented by non- destructive geomagnetic and geoelectric measurements with a reading distance of 0.5 m or less. The resulting images can be combined with supplementary information. Thus quickly and inexpensively further knowledge of the archaeological monuments may be gained by means of digital image combination. After choosing suitable instrument set-up and measuring parameters accuracy may be enhanced by adding data of GPR measurements and depth information. The presented interpretation methods allows us to incorporate GPR into the standardized interpretation process of archaeological - geophysical prospection. GPR and other available geophysical data being the basis, a detailed 3D interpretation model of monuments is created. The thus gained information is an extremely important and efficient tool for any further archaeological research. Empiric data resulting from special case studies and developed evaluation - and interpretation methods enable projecting of a specific strategy for overall prospection of Carnuntum. Such a prospection seems to be urgently necessary from the scientific as well as from the development-planning point of view and could give enormous input to economic strategies by bundled and focused actions for the largest archaeological zone in Austria.
Because of different limitations, e.g. time, instrumental or economic limitations, only single-method geophysical investigations are carried out in many cases. However, a single method is often limited by the capability of the utilized physical principles to display certain archaeological patterns. Therefore, an integrated geophysical investigation technique should be applied to overcome this problem. At Kal peninsula (Jutland, DK) an integrated geophysical prospecting was carried out to detect different subsurface targets related to the old medieval castle and its surroundings. To locate houses and the position of different defense structures, four different areas were investigated using geomagnetic prospecting, ground penetrating radar (GPR), geoelectrical profiling and surveying. By means of combined geomagnetic and GPR measurements the situation at the first entrance to the peninsula was investigated. To correct the GPR data for topographic effects, the topographic map was refined by dense surveying. Because geoeletrical profiling has generally a lower resolution than the other two methods, it was applied as a first prospecting method to find the continuation of the ancient road outside the forecourt. Afterwards, anomaly regions found by this method were studied in detail using GPR and geomagnetic prospecting. The data revealed the distribution of old farm houses in the forecourt and the position of the ancient road leading from the entrance of the forecourt up to the castle. A 3D-image of the urban plan of the area under study is finally presented.
Some years ago, very slowly decaying transient signals were measured during TEM survey over metamorphic crystalline rocks in the mouth of the Barun-Khal valley which is situated in the vicinity of village Chernorud, at the western shore of Lake Baikal. Being converted to apparent resistivity, these transients resulted in values of about 2 - 5 ohm-m. Since both in-field and laboratory DC resistivity measurements didn't indicate any conductive rocks evidence within the TEM anomaly area, the TEM results seemed to be confusing.
To elucidate the cause of the slowly decaying transients, parent rock and soil samples were studied in laboratory using: 1) microscopic examination; 2) small coil TEM measurements; 3) hysteresis and thermomagnetic analyses. It turned out that anomalous in-field measured transients were caused by the relaxation of magnetization of extremely fine ferri -and/or ferromagnetic particles concentrated in the near-surface layer. The origin of these particles for a long time remained a mystery.
In 1996, the third-year students of the Irkutsk Technical University that had in the vicinity of Chernorud their training in field geophysics, fortuned upon a gopher's burrow. Among the soil thrown out of the burrow, many slags and charcoal fragments were found, which suggested an ancient metallurgical activity. The slags were electrically nonconductive. Examination of slags with chemical, X-ray diffraction and SEM analyses has revealed that they consist predominately of a silica matrix with dispersed within it ultrafine particles of metallic iron, magnetite, phayalite, and wuestite. Being placed into a small coil, the slags produced slowly decaying transients caused by magnetic viscosity effects. By chemical and mineral composition the Chernorud site's slags proved to be identical to those which are known to have been formed during yielding iron in ancient bloomery furnaces.
The total magnetic field measurements carried out along two lines intersecting at the above gopher's burrow have indicated a positive magnetic field anomaly with amplitude of 50 nT, and 25-30 m in diameter. A reconnaissance excavation carried out to a depth of 0.8m over the 1m by 2m area centred at the gopher's burrow resulted in discovery of slags, charcoal, porous iron, and baked clays. In 1997, the excavation area and depth were increased up to 3m by 4m, and 1m, respectively. This time, remains of a bloomery furnace, some pottery sherds and other artefacts were found.
In 1998, magnetometry data were collected over a rectangular, 200m by 150m area centred at the excavation. Magnetic field measurements were taken at 2m intervals along parallel profiles spaced by 4m. The magnetic field contour and surface maps exhibited two positive isometrically-shaped anomalies connected via a narrow "cross connection". Unfortunately, the gopher's burrow and excavation fell just within the "cross connection" rather than within one of the main anomalies. The following excavations are planned to be taken in central parts of the above anomalies.
Radiocarbon dating of three charcoal fragments sampled during the excavation from different depth intervals has given ages of 1915 35, 2050 35, and 2180 30. These results make it apparent that iron age at the western shore of Lake Baikal started about 700-900 years earlier than it is generally appreciated. Note, that anomalous transients were measured over an area of no less than 15 ha. This suggest that iron yielding in the Barun-Khal valley was performed on a large scale.
The first pioneer magnetometric measuring on archaeological sites in Czechoslovakia were realized in the late 60´s. The various kinds of proton magnetometers and also methodologies of archaeomagnetic prospection were applied on different types of Czech, Moravian and Slovakian archaeological sites and in particular features for more than 25 years. By present eyes of archaeogeophysicists it has been the time of many very good results of small magnetic surveys which were mostly aimed at the individual interest of archaeologists and their archaeological excavations. Geophysics in archaeology has been often observed and also used during that time only as a service prospection method of archaeology. Another more intensive application of geophysics before rescue archaeological activities and excavations started in this country in the beginning of 90´s. Since that time it has been more real to start also another aimed cooperation of geophysics within other methods of archaeological prospection and also archaeological research. Archaeomagnetic methods were than more systematically connected, for example into the project of aerial prospection and its verification, project of surveys of abandoned medieval glass-working sites or into the landscape reconstruction project within application of intensive field walking methods. ...Due to this intensive individual cooperation and putting geophysics into the Department of Landscape Archaeology of Institute of Archaeology in Prague then could Bohemia start the new era of more systematic archaeological and also archaeogeophysical projects based on the use of proton magnetometers and fluxgate gradiometers. The new archaeological project „Settlement areas of prehistoric Bohemia" (Gojda et al. 1997-2002, Institute of Archaeology Prague) offers new ways of wide and intensive cooperation of non-destructive archaeological methods (aerial prospection, geophysical prospection, landscape reconstruction, systematic field walking survey all together with GPS, GIS,…) for the systematic study and prospection of chosen intensively settled and used prehistoric areas/landscapes. The results on the poster demonstrate the new scales of use of modern caesium magnetometers for the study of the whole archaeological sites (atypically fortified prehistoric settlement sites, ploughed burial-mound areas) and connection of results with other archaeological methods. Another new archaeogeophysical project under the Ministry of Culture „The identification of destroyed fortifications and inner structure of settlement of hillforts" (Krivánek 1999-2000, Institute of Archaeology Prague) documents another application of caesium magnetometers for the detailed prospection of larger areas of abandoned hillforts which could bring new archaeological view on site, but also could help for better and more precise protection of whole archaeological monuments. Only the first year of experience with caesium magnetometer prospection has shown that for the Bohemian archaeogeophysics a new era of unexpected and many times impossible applications of method on large areas of sites as in detailed scale of individual types of features. Other cooperations of various archaeological and geophysical methods are also planned in Bohemia in some future interdisciplinary projects.
From 1993 up to 1998 archaeologists excavated a settlement near Mardorf. The investigated settlement Mardorf 23 is situated in the eastern part of the „Amöneburger Becken", an about 120 km2 extended basin in the middle part of Hessen in Germany. Because of the soil conditions (loess developed on clay) this region belongs to the upper most fertile parts of Hessen. Mardorf 23 seams to be one of the oldest German settlements in that region. Excavations showed, that this settlement has its origin in the Iron Age- and Emperor Age (about 50 B.C. up to 300 A.D.)
In addition to the archaeological studies also geological and geophysical prospections were done. To optimise the excavations, geomagnetic prospections were carried out. 1995 B.Zickgraf and M.Posselt started these investigations. They covered an area of about 16.000m2. Because of the good results, 1997 and 1998 we continued these measurements. Up to now an area of about 60.000 m2 is mapped with geomagnetic method. We worked with a Fluxgate-gradiometer FM-18 from GEOSCAN research (Bradford, UK). All the field work was done in the same manner. The distance between two points was 0.5 m and also the increment between the profiles was 0.5 m. The resolution of the gradiometer was not better than 0.1 nT/m. Because of a temperature drift, the data had to been corrected by a smoothing algorithm. This was done on the base of statistical calculations.
Fig. 1 shows the results of all measurements done in this region within a scale of ? 5nT/m. We can find out objects from different time scales. There are not only visible archaeological but also geological and also modern structures.
Especially in the south-eastern part we can see some linear structures which can be composed to polygons. Excavations have confirmed the assumption, that we have found geological structures which have been formed during the glacial period. These former ditches are now covered by a layer of about 1 m thickness. Younger geological elements can be seen in the north. From geological and archaeological studies we know, that the landscape has been changed in the past. The curved former border of meadow can be seen from west to east. In the north the covering layer consists of alluvial sand with variable thickness. That's why it seems to be unlikely, that archaeological structures in this area can be detected by geomagnetics. South of this border we see a lot of narrow restricted positive anomalies. They are caused by pits, holes and vestiges of states. The excavation has shown, that these anomalies belong to different time periods. Not only old German but also Neolithic marks are visible.
The sharp linear elements are caused by old field boundaries. Additional we see younger and modern structure. The more or less linear anomaly in the northern part of the investigated area is due to a modern field-path covered with basalt. Some metal causes the large anomaly in the south-east.
Acknowledgement:
We thank the colleges B. Zickgraf, M. Posselt, U. Spangenberg, N. Lieske and M. Eisenreich for their support during the field measurements.
Literature:
M. Meyer, Die Siedlung der Spätlatène- und Kaiserzeit von Mardorf, Fdst. 23, Vorbericht über die Ausgrabungen 1993 - 1994 Berichte der Kommission für Archäologische Landesforschung in Hessen 3, 1995/95, S.47-58
M.Posselt, B. Zickgraf Bericht über die geophysikalische Prospektion auf dem Fundplatz Mardorf 23, Gmde. Mardorf, Kr. Marburg-Biedenkopf vom 6.3. bis 9.3. 1995 (unpublished)
Georadar is now an established method for archaeological prospection and the advantages and limitations are known. If properly processed and migrated, 3-D georadar data can very accurately estimate the depth and size of structures in the underground. The potential of this 3-D mapping technique has not yet been fully exploited. The data are normally represented in the form of profiles (vertical slices), time- or depth-slices or a combination of these. Unfortunately these procedures allow only limited insight into the true 3-D structures. Attempts to overcome this problem by manual or semi-automatic interpretation are very time-consuming. The proposed solution to reveal the full 3-D structure is the automatic calculation of isosurfaces. This new method is robust and efficient and reduces the amount of data substantially, which makes it suitable for surveys of large areas. The information contained in the isosurfaces can be readily exported to GIS-, CAD- or virtual reality systems for further analyses and/or display. With these tools the results can be viewed from any angle to aid the imaging and interpretation, the dimensions of the structures can be extracted directly, and the results can be rendered to make them understandable even for non- specialists.
Bavaria is the largest state in Germany. In the last 20 years aerial archaeology has been practiced. For reasons of costs, the pilot has to also act as navigator, archaeologist and photographer. This method has proven to be the most successful and at the same time the least expensive. The beginning years were, for an eager pioneer visionary, very busy and with little time devoted to systematic research and the detailed processing of the aerial photographic material received. At that time flying activities were concentrated on regions which were suspected to yield many new finds. So much photograhs were taken that large amounts of the pictures lay unattended for a long time in non-functional archieves.
In the meantime, without losing the effectivness of detail, many improvements were instituted. It was realized that the amount of aerial photographs alone were no criterion for the quality of aerial photograph prospection methods. Only when a usable amount of photographs were made available to the archaeologists in a short time was one able to speak of effective aerial archaeological photography. For that a well supplied archieve with properly trained personnel and necessary equipment is most important. Qualified personnel are extremely necessary in order to have an error-free and properly functioning archieve. Wrong archiving often leads to the temporary loss of photographs which often are found suddenly after a long period of time. Continuous communication between the archaeologists on the ground and the aerial archaeologist is very important in order to fulfill a concrete need for aerial photography in a very short time. The advance preparations for the prospection flight have been very much improved in recent years. Meanwhile some of the flight projects have been mapped from known archaelogical sites seldom flown over where many new sites have been located. This tiresome project over not so promising regions does not indicate a large amount of new findings like those that appeared in the beginnig years, but do give a large amount of scientific and other important information.
In addition to the project intense flying always indicates enough possibilities to control already known finds and document any changes in their condition. Even with all of the preparatory work on the ground, a little luck is always needed in aerial photographic prospection due to different factors like weather, flying route, time of day, viewing direction, shape and changes in growth of land characteristics. Many of these factors must correspond with each other for new finds to be of value to all concerned.
Whim Plantation on St. Croix in the U.S. Virgin Islands was the site of a sugar mill operation from the early 17th to the late 19th centuries, and now houses the St. Croix Historical Society. In the spring of 1999 a multidisciplinary group from Michigan Technological University conducted geophysical surveys over the site of the sugar mill complex to highlight promising areas for a planned archaeological dig to be conducted in the summer of 1999. Ground penetrating radar, total field magnetics and earth resistivity were used. This area contains both subtle anomalies of buried foundations and small metallic objects as well as massive anomalies caused by very large buried and surface metallic objects. Interest lies not only in the easily identifiable anomalies but also in smaller anomalies hidden within the data. The complexity of the data required advanced processing and interpretation. The site was not only well suited to multiple geophysical methods, but required them. Each geophysical method could pick out large anomalies well, but confidence with subtle anomalies could only be gained through comparison with all three geophysical methods.
Since 1989, a vast geographic sector centred on the eastern part of the Armorique area which lies both in Brittany aud the Pays de la Loire region, is subject to systematic aerial prospections at low altitude. The conditions of detection, although fairly varied, do not constitute real obstacles to the discovery of vestiges. Due to the real regrouping of lands that began in the 1960's, the traditional bocage of western France has gradually been replaced by semi-open landscapes which are turning out to be the favorite haunt of aerial archeology.
Among the thousands of discovered sites, an overwhelming majority belongs to the category of enclosures bordered by sets of embankments and ditches,that have now been levelled and filled in. As a matter of fact, the vestiges kept above the grownd are few and belong most of the time to the medieval period.Concerning the Gallo-Roman monuments built on fundations that were lined with stones, there are hardly any. The chronological range is wide because all the major periods from Neolithic to the Middle Ages are represented.The nature of the sites covers the whole range of human manifestations pertaining to the conquest and the development of "local territories". The habitats, necropolises, roads and the patterns of fields are engineered to the extent of making up a rural fabric which is truly coherent, especially during the Iron Age and Antiquity. This has been particularly brought to light in the bassins of river Seiche and Oudon, which are respectively situated in the eastern fringe of the departement of Ille-et-Vilaine and in the south-west of departement of Mayenne. The third international conference on archeological prospection will give us the opportunity of presenting a serie of discoveries that, without being original, remain nonetheless fundamental for the knowledge of the stages of the ancient settlement in the western extremity of the European continent. In the recent years, the computerized dataprocessing has been applied to the rectifying of oblique aerial photographs and to the making up of cumulative cartography.
Finally the aerial campaigns are succeeded by ground verifications, excavations and boring which bring fundamental chronological data.
An important question in archaeological geophysical prospection is the separation between anthropic and natural geological features. Generally the archaeological features are near the surface so that it is possible to distinguish them from the natural ones through suited investigation depths.
It is well known that electrical resistivity prospecting is a good method for the adjustment of the investigation depth owing to the electrode spacing. But the investigation depth and the electrical image are strongly dependent on the electrodes arrangements. The "archaeological" arrays are the twin electrode, the pole-pole, the square, the Wenner ??and the Wenner ?. In this paper it is shown that the pole-pole yields a very good discrimination between shallow and deep buried features. The pole-pole array is an improvement of the twin electrode (1) in the sense that remote electrodes are far from each other so that the readings provide the true apparent resistivities without any problem of continuity between adjacent grids.
The physical basis of the behaviour of the pole-pole array can be deduced from synthetic results about the anomaly created by a small body on a pseudo-section. Indeed, when comparing the anomalies of a small body imbedded in homogeneous ground obtained with several archaeological arrays, one sees that the pole-pole anomaly has a better resolution in the horizontal direction and also in pseudo-depth (2). This advantage of the pole-pole over the other arrays for depth discrimination is reinforced by two other properties: its technical simplicity (only two mobile probes) and its largest investigation depth (3). Thus, for a given investigation depth, the pole-pole array has the smallest dimensions of all arrays. We show that multi-spacing pole-pole maps allow an efficient vertical filtering of anomalies in cases which would be otherwise hard geophysical problems. Case histories are the search for ditches in karstic geology, the detection of stony burial structures on very shallow resistive substratum, the separation of superimposed structures in a Roman town (4) or, on the country, the proof of the absence of any buried anthropic structures.Abstract=References
In geomagnetic survey, we usually measure the magnetic field only on one 2-D plane. In this study, the authors will propose the method of reconstructing the 3-D distribution of the magnetic field data from the 2-D magnetic field data and its application to estimate of the shape and the depth of the magnetic bodies. For example, in the case that two magnetic bodies are buried and one magnetic body is just above another one, only one magnetic anomaly is observed on a horizontal plane over these bodies. However, if we could assume a vertical observation plane in the ground and obtain the magnetic field data on the plane, we would find two magnetic anomalies on this virtual plane. The magnetic field distribution on z=z1 plane can be calculated from the magnetic field on z=z0 plane using 2-D Fourier transform as , where Bz0 and Bz1 are magnetic field on z=z0 and z=z1 plane, F[ ] is the 2-D Fourier transform, k=(kx,ky ) is the 2-D wavenumber vector and z0> z1. Applying this equation repeatedly to the 2- D magnetic field data on 2-D planes with various inclinations, the 3-D distribution of the magnetic field data in regular region can be reconstructed. Assuming an appropriate plane in the 3-D space and applying the reduction to the pole technique to the reconstructed magnetic field data on the plane, we can estimate more accurately the shape of the magnetic bodies. The Fourier spectrum of the magnetic field data produced by one magnetic body in logarithmic scale is presented as Constant, where z' is a depth of the magnetic body, z0 is a vertical coordinate of the observation plane. Thus, we can estimate the depth of the magnetic body from the inclination of the logarithmic spectrum of the magnetic field data. However, if there are many magnetic bodies, it indicates only the depth of the shallowest body. In this study, the authors will propose the method to determine the depth of these magnetic bodies even if more than one magnetic bodies are buried in different depth. In a simple case that two magnetic bodies are buried in different depth, as the observation plane is inclined with angle ?, each distance between the observation plane and the magnetic bodies changes. At a particular angle ?*, these distances are equal to each other. So, the depth of both magnetic bodies can easily calculate from the angle ?* geometrically. For example, two magnetic dipoles are buried shown in Figure 1. The Fourier spectrum of the magnetic field data on z=0 plane is shown in Figure 2. Figure 3 shows that the inclination of the logarithmic spectrum of the magnetic field data on the virtual observation plane varies as the inclination angle of the plane is changed every 1° between 40° and 50°. We can easily find a bending point at ?* = 45° in figure 3; then, we can estimate the depth of each body.
The aim of the paper is to illustrate a system of acquisition, elaboration and interpretation of data obtained by geoelectrical prospecting in the upper level of the ground for archaeological research. The energising equipment furnishes an ac sinusoidal current with frequencies between 40-380 Hz. The generator has been realised with two tension outputs to utilise two different energising dipoles during the survey, in this way it is possible to elaborate data in a tensorial form to obtain apparent resistivity maps in conformity to the actual anomalies distributions. Measurements are taken over rectangular areas using two dipoles of different sizes which are fixed perpendicularly on a mobile frame. In this way, for each measurement point, it is possible to evaluate two different components of the induced field. (The current probes are kept in the same place while all the voltage measurements were taken in the chosen area). The method proposed allows the measurement to be taken quickly, no induction effects are shown in the cables at the above mentioned frequencies interval. The acquisition system is based on a PC with a 16 bits card, a filter-amplifier provides to eliminate natural and artificial disturbances, without filtering it is possible to acquire four temporal series obtaining SP and geoelectrical measurements For each measured area a software was developed under the PC environment to perform the invariants map of the apparent resistivity tensor, directly in the field.
The combination of geoelectrical mapping and sounding using modern multi-electrode resistivity meters can give dense information about underground structures and layers. Usually axial electrode arrays - e.g. Wenner or dipole-dipole - are applied. A crucial disadvantage of an axial configuration is the bad resolution of complex 3D structures. Improvement may be achieved by application of square arrays. But geophysicists shouldn`t stop halfway.
Only considering specific resistivity ? as a tensor (?ij) results in a real improvement of the resolution of square array measurements. Tensor measurements and 3D inversion allow a determination of boundaries of complex 3D structures - resistive bodies like air-filled cavities or foundations as well as conductive ones like fillings of pits, cellars or water-filled cavities.
Examples for model estimations by FD algorithms and tomographic inversion of the specific resistivity tensor show the large possibilities of DC tensor geoelectrics compared with conventional electrode arrays. A field example - the investigation of a gallery digged into a loess layer - is given.
The circular ditch system of Glaubendorf II was detected by aerial archaeology and is situated north of Vienna in Lower Austria. The monument lies on a slightly sloping terrace of the river Schmida. The site situated in loess soil is already heavily eroded. A first interpretation of the aerial evidence showed three concentric ditches and six regular entrances were suggested. A first archaeological excavation in 1986 opening a small 70 m trench proved the triple ditch monument with a single inner palisade as to date to the Middle Neolithic (4800-4500 BC).
The site was magnetically prospected in spring 1998. The magnetic survey covered 4.28 ha and was measured in a 0.5 x 0.125 m raster using a PICODAS MEP750 multisensor cesiumgradiometer with 0.005 nT resolution. The magnetic data was visualised as digital image and georeferenced for archaeological interpretation. The digital image representation shows a triple circular ditch system surrounded by various pits indicating the last remains of the former settlement. The circular ditches with diameters of 71, 90 and 109 m are 3.5 to 4.5 m wide. They are interrupted by five entrances. The monument was actually constructed on a regular hexagon, but the sixth entrance was only built on the inner ditch and was dug through later. This could be shown by 3D modelling of the ditches and the according 3D reconstruction of the monument. In the centre a 2000 m2 free area was surrounded by a palisade 53 m in diameter with only two entrances in the east and in the west. The palisade is only partly visible in the magnetogram due to erosion. In magnetics the area already excavated in 1986 no longer shows the traces of the palisade. Looking at the excavation results we have take in account a mass of at least 40 cm eroded during the last 12 years. Due to this rapid erosive processes geomagnetics is the only way for the documentation of these oldest monuments in Middle Europe. More then 30 of them are situated in the Eastern part of Austria and half of them still awaiting geomagnetic prospection.
The site of Puch / Kleedorf near Hollabrunn north of Vienna is known from aerial archaeology. It is situated on gravel and sand overlain by loess and covers 25 ha. The aerial evidence shows a lot of pits and two circular ditch systems. These circular ditch systems may be dated to the Middle Neolithic (4800-4500 BC). The archaeologiocal remains show impressive polychrome painted pottery of the Lengyel culture. The most striking expression of the high cultural level of this farmer society are the monumental circular ditch systems situated inside large settlements. These oldest monumental buildings in Middle Europe are formed by up to three concentric circular ditches 40 to 180 m in diameter. The ditches are 4 to 8 m wide and always show a typical V- shape 3 to 6 m deep. They normaly have regulary situated interruptions, the entrance inside the monuments. The centre is enclosed by one to five rings of palisades but lack of any other archaeological remains which could help to understand their purpose.
The circular ditch systems Puch and Kleedorf are situated in closest neighbourhood. The distance of the centre of the double circular ditch system of Puch to the single one of Kleedorf is 260 m. They were magnetically prospected using high resolution cesiumgradiometers. The site was archeologically interpreted based on GIS combining aerial photos and geomagnetics. The digital terrain model measured from the aerial photos was combined with 3D magnetic modelling results to produce a comprehensive reconstruction of the site using prospection results.
The magnetogram of Puch shows two concentric ditches with 83 m and 60 m in diameter, two entrances and the trace of an inner palisade enclosing a central area of 1750 m2. The southern part of the monument is already seriously destructed. The northern ditches are up to 4.5 m wide. The magnetogram of Kleedorf shows a single circular ditch 100 m in diameter formed by single segments of varying length. Again the centre is enclosed by a concentric palisade too. The central area of this monument measures 5550 m2, exactly the overall size of the monument Puch. The segments of the ditch are up to 40 m in length and partly up to 6 m wide. All around the two monuments many pits could be detected by the magnetic survey as well as by aerial archaeology.
The site of Puch was selected as reference site for testing new magnetic equipment and processing methods. It could be taken out of agricultural use. The site was already prospected using various grids from 0.5 x 0.5 to 0.125 x 0.125 m, different gradients from 1.5 to 2.85 m, resolutions of 0.1 and 0.005 nT producing digital image representations for easy comparison of the various results. Further comparative work is planned including electromagnetic methods and GPR as well as further magnetic surveys carried out with other magnetometers by various prospection teams.
Geophysical prospection of Roman villas is one of the major interests of archaeologists working in the former Roman provinces Pannonia, Noricum and Raetia. We present various sites situated all over Austria in different geological context. All of them cover at least 3 ha and might be situated in grass land as well as ploughed fields.
The villas were prospected by an integrated approach using high resolution cesiumgradiometers (0.1 to 0.005 nT / 0.5 x 0.125 m grid), multiplexed RM15 resisitivity meters (0.5 x 0.5 m grid, a=0.5; 0.1 m) and PulseEKKO 1000 ground penetrating radar (GPR) (0.5 x 0.05 m grid). Magnetics is mainly used to produce a large scale (> 5 ha) overview of the sites overall structure combining main buildings, economical buildings, roads, field system and the very often nearby cemetery. Selected parts of the magnetically prospected area indicating walls are additionally surveyed using resistivity mapping and/or high resolution GPR. As the resisitivity contrasts of walls are much higher than their magnetic contrasts they show up very clearly. GPR adds important 3D information on the detected buildings. GPR is adaequately applied to this type of Roman monuments i.e. data is measured in 0.5 x 0.05 or 0.5 x 0.1 m raster using 450 MHz or 900 MHz anntennas and with digital recording of the data. While magnetic and geoelectrical methods are standardly applied and widely accepted, the archaeological application of GPR still suffers from insuitable survey logistics, data processing, visualisation and interpretation techniques. The theoretically high archaeological potential of the method so far could not be presented to the archaeologists convincingly. GPR produces large amount of data with high information density. Visualisation of data mainly is done in B&W or colour coded representations of received amplitudes by time and distance in single sections known as "radargram". These representations of single sections show typical diffraction and reflexion patterns and are not easily understandable. One even could assume that it is nearly impossible for lay-men or unexperienced archaeologists to interpret anything in such a radargram. To use the high archaeological potential of this method new techniques of processing are necessary for producing objective and reproducible results. One of this techniques is the use of horizontal time slices as regular GPR data representations. Such a time slice is created by summarizing (or averaging) the reflected energy of the radar waves over a time window at any discrete reading of the regular or irregular measurement grid. We consequently propose here the use of a 3D data block of summarized amplitudes. This block might be cut through in any horizontal or vertical direction. The pile of horizontal time slices from GPR data might be animated for exploring the data. Magnetic, resisitivity and GPR data are visualised accordingly as digital images and combined in a GIS for archaeological interpretation by thematic mapping and attributal description. Based on the archaeological evidence derived from the combined interpretation of the geophysical results we produce a 3D archaeological reconstruction of the roman villas, presenting a comprehensive archaeological interpretation model. These models based on geophysical prospection data might also be animated producing understandable presentations of our heritage concealed beneath the surface for archaeologicts as well as lay-men.
Asparn a.d. Zaya 50 km north of Vienna is a well known settlement from the Early Neolithic culture of Linearbandkeramik situated in loess soil with low susceptibility. The site was recovered by aerial archaeology and is already partly excavated by annual campaigns since over 15 years. The site covering 25 ha was magnetically prospected during the last years using cesiumgradiometers with 0.1 and 0.005 nT resolution. The latest surveys carried out with a Multisensor Caesiumgradiometer in 0.5 x 0.125 m raster recovered typical remains of the Neolithic longhouses. Even the traces of single posts were resolved by the magnetics. The magnetic data (over 1.5 million readings) is visualised as digital image. For archaeological interpretation the data is resampled on 0.125 x 0.125 m raster and georeferenced using GIS software. The archaeological interpretation is done by thematic mapping and attributable description using the GIS ArcView.
The archaeological analysis of the geomagnetic evidence shows at least three main periods of occupation. Two of them were fortified by ditches 4 - 6 m width and up to 3 m deep. Several entrances inside the fortification are visible in the magnetogramm. The ditches form an oval central ditch system with an outer and an inner ditch which partly run in parallel and a trapezoidal enclosure appended in the north. Due to the high resolution of the magnetic data it was possible to interpret several typical longhouses of the Early Neolithic inside the plenty of pits of various size. The analysis of the orientation of the houses found by magnetics confirmed at least two periods. The settlement slightly moved from the bottom to the top of the hill. The excavation results showed the fortified settlements are the youngest. The occupation of the site dramatically finished 4950 BC by a massacre as the remains of the killed inhabitants were found at the bottom of the ditches.
Occasionally an earlier settlement from the germanic period (200 - 400) was detected at the lowest terrace of the river Zaya. The magnetic pattern of that settlement is clearly different from the Neolithic one. Several typical grubenhouses could be detected. The site of Asparn a.d. Zaya is already heavily eroded due to modern agricultural use as could be shown by aerial photographs, susceptibility profiles, the magnetic evidence and the excavation results. For the documentation of the rapid erosion process a partial remeasurement is planned after 10 years.
In the GPR method, the penetration of microwaves strongly depends on the soil conditions, and especially on the soil wetness. Soil wetness increases conductivity and thereby attenuates propagating radar waves. For accomplishing deeper penetration, an experimental survey has been carried out on Iki-Island, Japan, at a site where a channel was constructed 2,000 years ago for connecting a small port to a river. The channel is currently buried in a highly water saturated paddy field by up to 3 meters of soil. The soils currently within the buried channel and those buried below the channel floor are both primarily clayey wet soils. A GPR survey using a 400 MHz antenna and a recording window of 200ns was conducted on the site. The effective depth of relatively noise free reflections was down to about 100ns or 3 meter depth. Special gain settings for the recorded signals and post-processing filtering of the radargrams was performed on the data prior to applying time slice analysis. For helping to corroborate the GPR results, EM methods were used as a comparative study. The results using EM31 instrument with a 3.6 meter coil spacing show very similar results recorded on GPR time slices between 80-100ns.
The Argonne is a region in the north-east of France that is very well known for two reasons. First of all, it was an industry of Roman-age terra sigillata slipware, secondly the region was ravaged in the First World War. The area covers about 700 square kilometres and has several valleys running roughly north-south that cut through a chalk bedding.
The French government has plans to develop the region. Prior to the development a large scale archaeological prospection took place. It was coordinated by Sander van der Leeuw from the University of Paris. The work started in the summer of 1996 and was finished in the autumn of 1998 covering 6 field-campaigns of one month each. The work was carried out at 4 levels.
The results from the field-walking, the geophysical surveys and the pottery analyses were then imported back into the GIS, so a new analyses could be carried out. These new analyses were then used to guide the following field walking and geophysical surveys. This iterative process made sure that a full representative sample of the region was prospected taking geology, hydrology and height into account.
In total 7.5% of the total 700 square kilometres were field walked, 32 sites were surveyed with geo-electrical and magnetical measurements covering a total of 47 hectares. With the help of students from the University of Utrecht, department of geophysics and the University of Patras in Greece, some geophysical experiments took place at several sites, trying to extract as much archaeological information from the discovered sites as possible. Many of the measured sites were also augered and the combination of the multiple measurements and the augerings resulted in some remarkable archaeological information on the oven-sites.
Due to the integrated techniques and zooming in from large-scale surveys into close detailed inspections, a result was obtained that offers a good insight in the archaeology of the complete region.
The Roman province of Dacia was occupied by the Romans for about 150 years. During these years the province was the northern frontier and therefor very well guarded with Castella and wall-ditch systems.
The University of Nijmegen in The Netherlands were invited by the Museum of Art and History in Zalau, Rumania to carry out a pioneering archaeological prospection. Two sites were selected for the fieldwork: the Castellum of Tihau and the Roman city of Porolissum. The Castellum was selected because previously some roof-tiles were found at the site carrying the markings of the "Cohors I Cananefatium", Dutch tribal auxiliary forces in the Roman army, therefor linking the Roman history of this Castellum to today's Dutch University of Nijmegen. Furthermore, previous trial-excavations proved that the site was relatively undisturbed and offered good opportunities for an extensive prospection. The city of Porolissum was selected because it has a vast fort and a civil Vicus of unknown size. Small trial-trenches covering a wide area prove that it must have been a very large city, but so far the full extend is still unknown.
The work consisted of height measurements, field prospections, augerings, trial trenches and geophysical measurements. Geophysical measurements were carried out by RAAP- archaeological consultancy with the assistance of two students from the University of Utrecht, department of geophysics. The methods used were geo-electrical and magnetic measurements using Geoscan equipment.
At the castellum of Tihau the prospections resulted in a clear image of the construction of the castellum and the building within the castellum itself. The geo-electrical measurements show nicely the rectangular stone constructions of the wall with rounded corners, the gates and defensive towers, the roads, the horreum, the principia and the praetorium. Remarkable information was obtained from the difference between the geo-electrical measurements with an electrode spacing of 50 cm and the geo-electrical measurement with an electrode spacing of 100 cm. Some structures like the praetorium only show up at the 50 cm level, but the gates and the food-storage show up in both. The magnetic measurements show clearly the wooden barracks structures and some ovens lying outside the castellum. Due to the usage of multiple techniques, additional archaeological information was obtained and this fortress can be considered as one of the best studied Castella in Dacia. The figure shows the result of the geo-electrical measurement with an electrode spacing of 50 cm.
The results in the city of Porolissum were not as clear as expected. Some linear structures could be interpreted as roads, some structures might be related to houses. The very steep slope of the hill is certainly to blame for the blurry images.
Aerial survey and field walking of a freshly ploughed field lead to the discovery of a new site in 1981: the Galgenberg near Kopfham in Lower Bavaria. To find out more about the size and extent of the site a survey was carried out by Dr. Helmut Becker, of the Bayerisches Landesamt für Denkmalpflege, Munich, using for the first time in Europe the highly sensitive caesium magnetometer. The measurements, taken manually at 1m intervals, indicated complex ditch systems with several features inside and outside the enclosures. The main, oval enclosure seemed to have one entrance with foreworks lying directly in front of it. It was this plan that guided our subsequent excavations at the Galgenberg for the next nine years. A subsequent caesium magnetometer survey, taken semi-automatically at 0.5m intervals with digital graphic evaluation, gave a much more detailed picture of the main enclosure. Constant comparison of excavation and caesium magnetometer results led to improved, fully automated data collection and digital evaluation now widely used by Becker and his team. This method was used to produce a survey covering a large area on the Galgenberg, indicating the presence of at least six enclosures, which might otherwise have remained undetected. Although the magnetometer survey had provided the 'blue print' for the excavation it was only by excavation that the full extent of the complexity of the prehistoric remains and their relationship to one another became clear (Ottaway, 1999). For instance, the forework to the entrance, suggested by the caesium magnetometer survey to be a relatively simple structure, had undergone at least three major structural changes. These had transformed the entrance from one surrounded by a cluster of square features to an entrance which was most probably embellished and strengthened by two forework buildings which were arranged in such a fashion that entry into the enclosure was by two or three relatively narrow gaps left between the forework structures and the ditch. Entry into the enclosure was much more controlled than before and could, if necessary, be defended easily and effectively. The forework and some of the structures around the terminals of the ditch had been whitewashed, which must have given additional visual impact. The result must have been imposing, restricting vision and movement into the enclosure. It was more of a statement of control, protection and defence than it had been for previous generations. Deposits in many of the other features inside and outside the enclosure speak of phases of decommissioning and deliberate deposition of artefacts, followed by destruction horizons and a shift in the nature of deposits. To conclude, only through the complementation of prospection and excavation can the full picture of the prehistoric landscape and the sites contained therein be explored.
Reference
B.S. Ottaway 1999 A Changing Place. The Galgenberg in Lower Bavaria from the fifth to the first millennium BC. BAR International Series 752.
The routine application of geophysical prospection for archaeological subsurface structures have been established during the last decades. Major benefits arise from the fast and non- destructive documentation of archaeological objects even on large areas. Most common, magnetometer surveys with hand held fluxgate magnetometers are carried out. Beside this, resistivity, electromagnetic and ground penetrating radar (GPR) measurements are used, when investigation sites are not suitable for a magnetic survey. Here we want to present the results of two surveys on Early Midage grave yards in the cities of Weinstadt and Kirchheim/Teck (Baden-Württemberg, Southern Germany). Both sites have been investigated with resistivity meters and GPR, respectively. In general the survey of single graves is relatively difficult, as the objects are quite small and the physical contrast to the surrounding subsoil is often very low.
Survey in Weinstadt - stone-lined Merowingian graves
A field of about 5000m2 was investigated for stone-lined graves, which were suspected there to some earlier archaeological investigations. Resistivity and GPR measurements have been carried out, as both methods seemed to be suitable to detect single graves, lined or covered with limestone rocks, in loess ground. An earlier magnetic prospection with a fluxgate magnetometer (FM36, Geoscan) yield no results on archaeological structures due to the local soil conditions.
The GPR survey with a 400MHz bistatic antenna (Ramac GPR, Mala) on part of the area yield no clear results. Hence, the total area was measured with a resistivity meter (RM15, Geoscan). We used the standard Twin Probe configuration with a mobile probe spacing of 0,5m. According to the small scale of the archaeological objects a narrow sampling interval of 0,5m x 0,5m was chosen. It was expected that limestone rocks (marking single graves) in conductive loess soil correspond with relatively high resistivity values. Figure 1a shows the result of the resistivity survey, together with the location of later excavated stone-lined graves. The data quality of the resistivity survey is less good in the eastern part of the investigated area due to the rough terrain there. Several small areas with local high resistivity values (green colours in Fig. 1a) occur in the middle and the east. Most of these areas correspond with a stone-lined grave, as the later excavation has shown. However, the graves without a stone frame were not detectable by the resistivity measurements. Although the resistivity survey was not able to resolve all stone-lined graves, the approximate position and extension of the grave yard was recognisable from the resistivity survey. Hence, the geophysical prospection has been a helpful tool in planning and execution of the archaeological excavation. An excavated Early Midage stone-lined grave is shown in Figure 1b.
Survey in Kirchheim/Teck - Alemanian graves
The investigation area, a meadow of approximately 1400m2, is located in the inner city of Kirchheim/Teck. The area is part of a large Early Midage grave yard, and over 100 single graves have been found at building sites in the vicinity. Magnetic measurements could not be carried out, as the area was partly lined with a several meter high metal fence. Hence, a resistivity survey (RM15, Geoscan) of the area in Twin Probe configuration with a sampling interval of 0,5m x 0,5m was carried out. According to the expected depth of the graves (0,7m -1,0m) a spacing of 1,0m for the mobile probes was chosen. However, from the resistivity survey only gross geologic features (changes in thickness of the alluvium) could be recognised. No indication on archaeological objects could be obtained, while the subsequent following excavation yield several graves at the investigated area. While the archaeological excavation was in progress, GPR measurements with a 400MHz bistatic antenna (Ramac GPR, Mala) have been performed over partly excavated graves. A radarprofile over two known graves is shown in Figure 2 (upper profile). At the right half of the GPR profile undisturbed, continuous sedimentary layering is visible. The graves clearly show up as zones of weak reflection with the sedimetary layering being interrupted. This pattern was assumed to be typical for graves at the local geologic conditions and further GPR measurements have been performed in the nearest vicinity of the excavation filed. Indications for additional graves were found at several locations, an example is given in Figure 2 (lower GPR profile).
Summary
In principle, resistivity and GPR surveys are suitable for the detection of grave yards or even single graves. However, graves without a stone frame or stone cover might not be visible in resistivity measurements. Surveys have be carried out with a high sampling interval and test measurements over already known graves are helpful. Nevertheless, the success of a survey still strongly depends on the local geologic conditions.
Hillforts have attracted archaeological interest for much of this century, and debate on their function and significance continues to be central to the academic study of the Iron Age. The term hillfort covers a multitude of different types of site and their varying sizes, morphologies and situations strongly suggest a range of different functions. Reliable interpretation of the role of hillforts in Iron Age society continues to be hampered by the small number that have been extensively examined archaeologically. Despite major investment in excavation of hillfort sites in Central Southern England, even here the majority of sites still remain a poorly understood resource.
Two years ago a major programme of archaeological geophysics was started by English Heritage in partnership with Oxford University to investigate a wide-ranging sample of hillforts (20 sites in total) in the dense hillfort zone of Wessex. The project was designed to build on the potential of rapid magnetometer survey for investigating hillfort interiors on chalkland geology shown by earlier surveys at sites such as Maiden Castle and in the Danebury Environs.
The project aims were to :
The project has revealed a wealth of new evidence for the nature of the internal utilisation of Wessex hillforts. While supporting some of the existing models of hillfort development, the surveys also show that the pattern is considerably more complex and varied than previously realised. A complete set of results from the project will be presented publicly for the first time and their interpretation discussed (discussion of significance of the results among participants will be very welcome as their interpretation is currently only at a preliminary stage)
If time permits, Wessex hillforts will be contrasted with geophysical results just obtained from the concentration of hillforts around the foothills of the Cheviots in the Northumberland National Park. The different geophysical approaches required to optimise the information recovered from these sites (of intrinsically different character to their Wessex counterparts) by nondestructive means will briefly be discussed.
As part of a wider research progamme of experimental archaeology at Callanish Farm, Isle of Lewis, Scotland, a number of experimental hearths were constructed, based on excavated evidence from the Late Iron Age houses at Bosta. Controlled and repeated burning of different fuel sources, for example well-humified peat, fibrous-upper peat, peat turf and wood was carried out over a number of burning episodes of three day durations.
A range of mineral magnetic measurements, including remanences and the variation of susceptibility with high temperature, were taken from the resulting ash samples. The high temperature susceptibility measurements show that the fibrous upper peat and peat turf have a single magnetic component, with loss of susceptibility between 570 and 600 $^{o}C$. In comparison the well-humified peat and the wood display a loss in susceptibility at significantly lower temperatures, with many samples having two distinct magnetic components. Stepwise discriminant analysis was performed on the room temperature magnetic data. A biplot of the resulting two main variables distinguishes between the four different sources.
Magnetic measurements were also carried out on hearth samples from two archaeological sites, Galson and Guinnerso, on Lewis. Comparison was made to the ash samples in order to determine if the fuel sources could be identified. Both the high temperature susceptibility curves and the discriminant analysis suggest that for the two selected sites the predominant fuel source was well-humified peat.
Measurements of in-situ and laboratory-based magnetic susceptibilities on material from the multi-period Old Scatness Broch site on Shetland, Scotland have indicated greatly enhanced soils. The enhancement in susceptibility is associated with midden deposits and is over one hundred times the susceptibility of surrounding deposits. In order to understand the origin of the enhancement and suggest causes for it, investigations were made to determine the nature and extent of the magnetic grains within the soils. A range of laboratory-induced remanences and susceptibilities, including the variation of susceptibility with high temperature, were measured on samples from three different areas within the site : 1. 67 samples were taken from two horizontal profiles through midden deposits within a circular post-broch structure. Discrete layers of deposition were visible within the midden. These midden deposits gave exceptionally high in-situ magnetic susceptibility values. 2. Five samples were collected from midden material deposited within a Pictish structure. 3. 88 samples were collected from a continuously sampled (at 2cm intervals) profile within a pit dug on the outskirts of the main settlement area. The profile extends through layers of midden, soil and sand material. In addition to determining the magnetic mineralogy and domain state of the magnetic grains, the magnetic data is also being used to compare between the different groups of material to gain an insight into changes in anthropogenic activity through time. For example, differences between the midden material collected from the circular structure and the midden material from within the Pictish structure are being investigated, which could give information on variations of fuel sources, industrial activities or burning processes between different periods.
Ground penetrating radar (GPR) and resistivity profiling provide potential routes to the generation of full three-dimensional geophysical models of buried archaeological sites. This paper reports on the development of field methodology for these two techniques in southern England, with the investigation of appropriate data processing procedures and the visualisation needs for presentation of the results in a form comprehensible to the archaeologist. These three interdependent aspects will be discussed with data examples drawn from a set of sites selected to give a broad range of site and sediment characteristics, including buried sarsen (quartzite) stones in the West Kennett Avenue, Avebury, a sarsen-chambered Neolithic long barrow with chalk mound, and the brick foundations of a late 15th Century Hall. The importance of appropriate procedures for topographic correction is emphasised, particularly where simple correction algorithms available in commercial software are limited in their applicability. Animation has a potentially significant role in the visualisation of multi-dimensional data, especially where data are available from complementary resistivity and GPR surveys.
The Linearbandkeramik is the culture of the earliest farmers in Central Europe (5500-4900 B. C.).The project „Bandkeramik Settlement History in the Mörlener Bucht"of the Johann Wolfgang Goethe- Universität Frankfurt/M. has the objective to learn to know more about the settlement-system of this culture and its history starting from the beginning of the using of the landscape for settlements, gardens and fields up to the collapse of its cultural system.
With this aim the project investigates the Bandkeramik settlement of a 60km² area of the settlement area called Mörlener Bucht between the cities Butzbach and Bad Nauheim in Hesse, Germany. The results of different archaeological field methods should be linked to the knowledge of the physical features of the landscape. The field work has a main stress on large-scale and non-destructive methods like intensive fieldwalking, in some cases providing the coordinates for each object, and surface plots of the topography linked with geophysical prospection. Only few excavations should be done to prove the character of selected features. It is the task of the geophysical prospection to investigate settlements in large scale. It should help to show their extension and structure. Up to now several large fluxgate-gradiometer surveys with more than 30 hectares at six different areas of investigation have been carried out.
Settlements, which are situated off the well investigated fertile landscapes or which seem to have a distinct function are of special interest. At the site of Wehrheim-Friedrichsthal, situated in a settlement area recently revealed, a first small magnetometer survey showed a typical ground plan of a Bandkeramik house with respect to its form. Several of such ground plans have been detected at the site of Butzbach-Fauerbach. One outstanding specimen is an almost completely preserved ground plan with a horseshoe-shaped ditch of the northwestern walls and several postholes, measuring about 40m in length. Furthermore features have become visible, which might be linked with the supposed exploitation of hematite in Bandkeramik times at this site.
In 1994 the Hesse Department for the Preservation of Monuments excavated a rich grave of the Early Latène period at the southern slope of the prehistoric hillfort of Glauberg in Hesse, Germany. The grave goods (gold torque, bronze wine-flagon etc.) lead to the assumption, that it was the grave of an important personality. In the course of further excavations an almost completely preserved statue of an idealised Celtic ruler or hero and fragments of three more statues were brought to light. These findings and excavations at the hillfort of the Glauberg proved that this site was an important place on the northern rim of the Celtic world, similar to the princely residences of southwestern Germany, northern Switzerland and eastern France.
In the first place aerial photography found hints for a barrow measuring about 50m in diameter being surrounded by a ditch. The excavation in 1994 confirmed this idea. Further weak traces of features were visible in the near environs of the barrow.
A first magnetometer and resistance survey following the excavation and covering an area of 1,5 hectares with the barrow in its centre showed very soon that it was included into a large system of ditches that enclosed the area in the Iron Age period.
Until now an area of about 110 hectares is covered by an even 0,5m grid-system using a fluxgate- gradiometer. The ditch-system localized up to now has an extension of more than 1,2km from east to west. Also visible are further ditch-systems of different age. Scattered over the whole area of investigation are several settlements of Neolithic to Iron age context inside and outside the large Iron age ditch-system.
The magnetometer survey at the Glauberg makes the special operation of geophysical methods among archaeological field methods clear (excavation, aerial photography, field walking etc.). Its potentiality and increasing importance in archaeology once again becomes visible.
Electromagnetic probing was conducted before excavation on baked areas and trampled areas at a number of archaeological sites. The studies undertaken were as follows:
(1) Magnetic surveys of a kiln site (13 - 14th century) Both a proton precession magnetometer and a fluxgate gradiometer were used and clear magnetic anomalies appeared in four areas. Excavation revealed that the appearance of these anomalies is related to the direction of the major axes of the kilns. Kilns with their major axis aligned north-south show quite a good correlation with magnetic anomalies, whereas kilns with an east-west alignment show a southward deflection of their anomaly patterns. When a proton magnetometer survey was done with low sensor height ( less than 5cm from the ground surface) quite clear anomalies were detectable on the kiln sites. Excavation showed that these anomalies correspond to the combustion chamber and the firing chamber of the kiln. As a result of being heated to a high firing temperature, these regions had acquired intense magnetisation (thermo-remanence) not only on the surface but at a deeper level as the magnetic properties of the baked soil confirm.
(2) Magnetic investigation at the Palaeolithic Ohara B site. Finding a hearth is important evidence for the existence of a dwelling from the Palaeolithic period onwards. We attempted a magnetic survey in combination with a rock-magnetic study for this purpose. At an artificially baked area by an open-air fire, both a magnetic survey and a test of the remanent magnetisation of the soil proved effective as methods of locating the slightly baked area. The Palaeolithic Ohara B site was studied using these magnetic methods, and a magnetically anomalous area was found suggesting the site of a fireplace. Another anomalously magnetised area was found by analysing the distribution of magnetisation in the buried soil. The remanent magnetisation in the soil showed a circular directional pattern, which could have been caused by a strong electric current flowing from the air into the ground. Such a pattern would be consistent with the spot having been struck by lightning. Thus, the soil retains evidence of lightning striking it in the Palaeolithic period. This suggests that the effects of lightning can be recognised using archaeological techniques.
(3) Electric resistivity surveys on trampled areas of the sites of building s at the Murodo Site (18th century) and Emashi- castle Site (15th century). Trampled areas such as the earth floors of house sites were identified as areas of high resistivity. By contrast, areas beneath the raised timber floors of buildings registered low resistivity. Such a clear difference may be caused by the degree of compaction and water content of the soil constituting the remains. Thus resistivity surveys are useful for studying the character of former buildings.
Southern Bavaria, embedded in a prealpine hilly landscape, possesses a lot of rivers,lakes, and swamps in the hinterland of the lakes. In similar situations of neighbour-regions, especially in Switzerland, Baden-Wrttemberg and in Austria in the Salzkammergut, has been detected a great number of prehistoric wetland sites. In Bavaria only a few sites are known until now. Nevertheless hundreds of hints are recorded. So it is an additional task of our team, to discover wetland sites and to examine them. We organize our work in projects.
A good example happened in 1997 and 1998, when the famous summerhouse of the bavarian kings on the small island, called Roseninsel, in the Lake Starnberg has been restored. A trench for electrics, phone and water was dug from the shore to the 500 m distant island. We decided to control earth-work on and nearby the island, which is well known for prehistoric finds and for a large number of wooden posts, some of them dated in UK and to try reconnaissance of further sites on the shore of lake Starnberg.
Documentation of the trench revealed the existence of a LBA- settlement, which was built on the shore of that time on pebbles and sand. On the island itself we discovered a small medieval castle. But the main purpose, to find out exact positions and dates of prehistoric settlements on the island, until then only known from sherds, could not be fulfilled successfully. The glacial dump has formed the island as a cone with steep sides running quickly under the sea-level. Prehistoric strata on the upper side of the cone were dried out and have been destroyed during earth work for summerhouse and park. However, preserved strata could not be reached in the trench. Drilling under the water-level revealed prehistoric strata until 3,80 m under the sea-bottom. With these data we have got for the first time ideas about postglacial sea-level changes in the lake Starnberg. As a result we could now define prehistoric water-levels, which depend from the level of known prehistoric sites, i.e. between 484 m . NNN. (recent level) and ca. 379,50 (level of late neolithic) As a next step we surveyed the recent shore until the water-level of 379 m with a side-scan-sonar. We recorded a lot of posts. Most of them are of recent age. Others seem to be older. They may be identified by GPS-position. In a few weeks we shall send divers to cut the posts . Then they will be dated in our dendrolab or, if not possible, by C14-analysis.
In my eyes, we have found an attractive not expensive way, to survey lake-settlements.
Besides the well-established ground specific parameters, magnetic susceptibility and apparent resistivity, the polarizability of the soil is another possible parameter for archaeological problems. The induced polarization (IP) bases on electrochemical processes in the subsoil that take place while an electrical current is injected into the ground. Consequently the resulting potential field at the surface is frequency dependent and reflects additional electrical properties of the soil. So far the method has been successfully applied for the monitoring of groundwater contamination and the distinction between clay and water-bearing rocks.
An application within the archaeological environment could be the detection of medieval wells containing wooden remains for subsequent dendrochronological investigations. Within the "Graduiertenkolleg Archäologische Analytik" supported by the DFG (German Research Foundation) our institute is developing a multichannel geoelectrics-instrument (SIP-256) that is able to measure both the apparent resistivity and the induced polarization-effect. By using an "intelligent" remote unit at each electrode the speed of the measurement has been increased tremendously. Thus the instrument enables fast mapping and sounding and a real-time visualisation of three-dimensional structures.
According to its mission of protecting and preserving the cultural heritage world-wide, UNESCO has provided funding for the geophysical investigation of buried archaeological remains related to World Heritage Sites in South Asia. During two pilot studies the response of buried features to standard geophysical prospection methods was investigated on selected sites in Bangladesh and Nepal in 1997.
The use of fluxgate gradiometers and earth resistance meters is well established in the developed world and the interpretation of geophysical anomalies as archaeological features is fairly well understood. However, very few geophysical surveys were undertaken on archaeological sites in South Asia and due to the climatic, environmental and geological conditions the geophysical signature of subsoil archaeological structures is markedly different. The specific problems encountered in the subcontinent will be exemplified with geophysical survey results from Bangladesh and Nepal (FM36 fluxgate gradiometer and RM15 earth resistance meter with twin-probe array).
Bangladesh is dominated by the alluvial floodplain of the Ganges with heavy Monsoon rain in the summer. As a consequence the non-perished architecture is dominated by solid brick structures with ornamental terracotta tiles which, as a ruin, manifest themselves as brick walls within brick tumble. Accordingly, magnetometer results are difficult to interpret. It was, nevertheless, possible to enhance the monument records of the World Heritage Sites of Bagherat and Paharpur considerably.
The survey of the sites of Tilaurakot and Ramagrama in Nepal showed much clearer evidence of buried brick foundations and provided insight into the layout of the ancient citadel and the stupa site, respectively.
Standard earth resistance surveys for archaeology normally use fixed electrode arrays to cover large areas. The features detected depend on the penetration depth of the probe arrangement and by combining surveys undertaken with various electrode spacings it is possible to investigate anomalies at different depths. Such data can be subjected to complex algorithms to calculate the actual resistivity distribution of the ground (tomography) or converted without further processing into values of apparent resistivity (pseudosections). This paper investigates how the simple use of pseudosections can provide images of the subsurface to aid the archaeological interpretation of sites. Efficient field techniques for cheap data acquisition will be reviewed and the responses to various electrode arrangements (twin-probe, Wenner, Wenner-broadside) illustrated. Data collection, manipulation and display are important issues when dealing with such data sets and case studies for the use of pseudosections, pseudoslices and volume visualisations will be provided. A major advantage of pseudosections is their minimal requirement for processing and basic data treatment tools (e.g. topographic adjustments, depth scaling) will be assessed. Pseudosections are an efficient tool for an initial evaluation of the third dimension (i.e. depth) and survey examples will be provided to show the validity of this approach despite limitations of the simplistic data treatment.
This is a provisional report of the research project entitled „Introduction to Aerial Archaeology in the Peoples Republic of China" at the Department of Pre- and Proto- History of the Ruhr University, Bochum in Germany. The project was started in 1995 with the aim of integrating aerial archaeology as an innovative method in the archaeology and the protection of monuments in China. It is financially sponsored by the „Stiftung Volkswagenwerk" and is based on close cooperation with the Chinese culture authorities and institutions on various different levels.
A research centre for remote sensing and aerial archaeology was founded 1997 in China at the National Museum for Chinese History (NMCH) in Beijing. This centre has now rooms and equipment for the interpretation of aerial photography, cartography, archives for aerial photography and maps. The fundamental tasks of this centre are: 1) to develop and research aerial archaeological methods and technologies; 2) to carry out over-regional projects in cooperation with archaeological institutes and institutions concerned with the preservation of historic buildings and monuments; 3) to support and look after the application of aerial-archaeological methods in certain regions: For example, the placing of work data such as maps an aerial photos, technical support, the training of professionals, etc. into the proper hands.
Parallel to these efforts to institutionalise aerial archaeology, from 1996 to 1997 many ground site projects were done in certain Chinese provinces to test and to prove exemplary aerial archaeology in actual practice. It was planned by means of this to collect methodical experience in different regions of China with differing climate, soil, vegetative and topographical aspects and not least the archaeological circumstances relating to these sites. This project was planned, prepared and carried out by the Department of Pre- and Proto-History at the Ruhr University, Bochum, in cooperation with the Chinese Ministry for Cultural Assets, the National Museum for Chinese History and relevant provinces.
The first result of these projects showed that the methods of aerial archaeology which have already been proved successful in Europe in carrying out aerial archaeology (with special focus on the discovery of underground archaeological sites), function just as well in China. The results, however provisional, are good for archaeological research and the maintenance of subterranean archaeological sites and especially to help persuade the archaeologists and the authorities for the preservation of monuments in China to use these new and effective methods.
Three selected projects are introduced under their relevant archaeological, methodical and technical aspects. They took place respectively in Linzi, Shandong Province (East China), in Gongyi, Henan Province (Central China) and in Chifeng, Inner Mongolia (North China).
The working group for archaeological prospecting at the department for geophysics at Kiel University (Germany) has undertaken several geophysical surveys on archaeological sites in northern Germany, Luxembourg, Italy and Turkey during the last years. Magnetic, electric, ground penetrating radar (GPR) measurements and shallow shear wave seismic were used for the investigation of Hittite, Greek, Roman and Viking age settlements, fortifications and temple constructions.
Primarily magnetic prospecting was applied for fast data acquisition in order to get a general idea of the subsurface remains of the archaeological site. Five Fluxgate gradiometer probes (Frster; dz = 40 cm), mounted on a portable rack, are carried by two persons along 50 meter survey profiles with a sampling interval of 5 centimetres inline and 20 or 40 centimetres crossline. The datasets were processed with the software Mar_Plot and presented as greyscale images. Striking anomalies are further investigated with geoelectric and GPR measurements. Therefore a multielectrode array and different GPR antennas (120, 200, 500 and 900 MHz) are available. Subsequent processing algorithms perform a 3 D view of the subsurface structures.
Prominent magnetic anomalies were found at the site of the Hittite town Sarissa in Central Anatolia, Turkey. Here 3000 year old ruins, located on a remarkable mound, were excavated. With the exception of few steep slopes the entire acropolis (150.000 m2) was investigated in the course of several survey campaigns (Fig. 1). The foundation of the 1.5 km long interior town wall surrounding the town centre was discovered and a distinct symmetric conception of the four ancient city gates was prospected. High uniform magnetic anomalies of the gate buildings insinuate a destruction by conflagration. The geomagnetic measurements were compared with geoelectric and GPR investigations at several locations. Our results show that the extension of the residential area is much larger than previously thought. The surveying of a sanctuary, found on a nearby mountain skid, revealed northward aligned buildings and the enclosure of an adjoining lake.
Magnetic and seismic measurements were applied for the investigation of the archaic fortification wall of Milet, located on a former peninsula at the west coast of Turkey. Nowadays the archaeological site is situated in the alluvium of the Menderes river. Milet's urban area included several ports and was enclosed by a town wall. Early settlements were found on a hill, called Kalabak tepe, in the south of the peninsula. We investigated the extent of the archaic city wall with geomagnetic measurements in order to examine the connection between Kalabak tepe and the lower part of the town. The rectangular street system, adopted by the Milesian Hippodamus, was detected and its orientation and size were proved to correspond with the excavated structures. The western coastline representing the border of the settlement was determined by the results of the magnetic survey . Some magnetic anomalies close to the ancient shoreline can possibly be identified as fortification or harbour constructions. Shear wave seismic was used to explore the structure of a harbour basin while magnetic investigations revealed the layout of the quay walls.
A recent feasibility study in the archaeological park of Selinunte, Italy, showed weak structures of buildings, street systems and the town wall, due to a low contrast between the used building materials and the surrounding subsoil. Further examples of the Viking age settlement Rerik at the Baltic coast and the Gallo-Roman settlement Wallendorf, close to the border to Luxembourg, will be presented in order to discuss the limits of geophysical prospection methods.
Future improvements may be possible with quick and precise positioning systems. Differential GPS promises an accuracy in the order of centimetres and is suited for the presented sites.
The present paper deals with the exploitation of the complex attributes of the magnetic signal in order to extract properties of the sources of the anomalous fields. Of course, the analytic signal comprises the most well known among them. The "local phase" and the "instantaneous wavenumber" comprise the other two quantities which lead also to source parameters mapping.
The analytic signal amplitude (Nabighian, 1972; 1974) poses some attractive features for any sort of magnetic prospecting. Its advantageous "geophysical" property is that is peaks exactly over the edge of the buried dipping contact that causes the magnetic anomaly. Also, its amplitude is independent of inclination, declination, remanent magnetization and dip if the sources are 2-D. With respect to archaeological Geophysics, the only disadvantage is that the analytic signal anomalies are relatively much broader than the lateral extent of the buried target.
The aim is to delineate the edges of the buried bodies, to estimate their susceptibility contrasts, to assess strike angles and produce burial depth estimates all at once. The complex attributes analysis offers the means to carry this out. It is exactly their applicability and effectiveness in exploring the subsurface for buried antiquities which is investigated in these pages.
The analytic signal amplitude for the simple contact model which produces the magnetic total field, T, is ... (1) and the local phase, i.e. the phase of the analytic signal for any particular location is ... (2). The local frequency is defined as the rate of change of the local phase, but customarily the local wavenumber is used ... (3). If we substitute the expressions for the vertical and horizontal gradients of the anomaly produced by a sloping contact Nabighian (1972) into the local wavenumber formula (3) yields ... (4) where h is the burial depth (Thurston and Smith, 1997; Smith et al. 1998). If we define the coordinate system such that x=0 directly over the edge, the maximum occurs at the same point and offers a means for burial depth estimation since at x=0, then ...
Thurston and Smith (1997) devised a technique to estimate the local dip and local susceptibility contrast as well by means of equation (3). That is d=theta+2I-90 again at x=0. The local susceptibility is obtained by ... (6). A useful model in various geophysical applications is the slab which also serves in archaeological Geophysics. For instance, a mesh of ruins which the archaeologists call "destruction phase" can be modelled as a magnetic slab. The same applies in some cases for structures like kilns, pits, tombs. The slab used here is buried at 1 m depth, its thickness is 0.5 m and its susceptibility contrast is 0.0005 (SI).Figure (1) shows the recovered local strike estimates of this source. The plane view of a slab is also shown in the same figure. The edges are completely delineated and strike angles recovered give a clear idea of the shape of the target.
REFERENCES
Nabighian, M. N. (1972). The analytic signal of two-dimensional magnetic bodies with polygonal cross section: its properties and use for automated anomaly interpretation: Geophysics, 37, 507-517.
Nabighian, M. N. (1974)Additional comments on the analytic signal of two-dimensional magnetic bodies with polygonal cross section: Geophysics, 39, 507-517.
Smith, R.S., Thurston, J.B., Dai, T.-F. and McLeod, I.N. (1998). ISPTITM - the improved source parameter imaging method: Geophysical Prospecting, 46 (2), 141-152.
Thurston, J.B. and Smith, R.S. (1997). Automatic conversion of magnetic data to depth, dip, and susceptibility contrast using the SPI ™ method: Geophysics, 62 (3), 8-7-813.
Blast furnaces were introduced into England towards the end of the Medieval period. This paper investigates the use of geophysical surveys for the interpretation of two prominent blast furnace sites in Yorkshire.
A predecessor of such blast furnace, a high bloomery, was revealed by geophysical surveys in Bilsdale to the north of Rievaulx Abbey, North Yorkshire, operated by the Cistercian monks. When the abbey was dissolved in 1538, the new landowner is known to have established a blast furnace in Rievaulx village. Geophysical survey work identified the finery / chafery complex, where the cast iron was processed, with slag tips, charcoal stores and leat systems. Combined with topographical survey work, limited excavations and documentary evidence the approximate location of the blast furnace in Rievaulx village was identified. The geophysical work is limited to open spaces between post-furnace housing and other physical constraints. However, it has been possible to identify the ore-roasting area and the likely source of water for operating bellows.
A second blast furnace site, in the Bretton Sculpture Park, near Wakefield, West Yorkshire occupies a green field site. A leat entering and leaving the site and a slag dump are the only pronounced earthwork features. Slag, burnt ore and charcoal are present in the soil. The blast furnace was operated in the 18th century by the same Yorkshire partnership who were also associated with a second furnace at Rockley, located 10 km south of Bretton. During the 1980s, the Rockley furnace, which is upstanding, and adjacent casting floors were investigated. By applying information from the Rockley excavation and the geophysical results from Rievaulx it has been possible to produce a very accurate interpretation of the Bretton furnace survey.
In August 1993 the section „Geophysics" was established at the Landesamt für Archäologie as part of the section „Naturwissenschaften" (Sciences). Legal basis for the protection of archaeological monuments in Sachsen-Anhalt is the „Denkmalschutzgesetz" (the law for protection and preservation of ancient monuments).
The geophysicist at the LfA supports the archaeologists before and during excavations with detailed mapping of archaeological structures indicated by archaeological aerial photographs. Main objective of geophysical mapping is to locate and document monuments with high precision in order to support their protection
Geomagnetic and resistivity mappings are carried out with a fluxgate-gradiometer FM36 and a resistance meter RM15 (Geoscan Research, Bradford, England). Since 1993 nearly 20 monuments have been mapped.
Following projects will be presented in detail: Geomagnetic plots reveal a circular enclosure with three entrances and two interior palisades at Goseck, Landkreis Weißenfels. The circular monument has a diameter of approximately 36 meters and is probably of Early Neolithic Age (Trace Plot). A curvilinear double ditched enclosure (Late Bronze Age?) was discovered beside the River Bode near Wegeleben, Landkreis Halberstadt and geomagnetically documented (Shade plot). The site of the totally vanished castle „Gottau" in the Elbe-river plain at Ranies near Magdeburg, perhaps 12th-15th century A. C., was geoelectrically mapped with a method 1m- twin with a raster of 1 meter (Special Shade Plot).
A discussion of the processing and presentation of geophysical data from a range of sites (UK, USA and the Middle East) is made using a new release of the program package Geoplot 3.0 for Windows from Geoscan Research. This package can process and present data from a variety of instruments including : resistance meters, gradiometers, magnetometers, EM instruments, and magnetic susceptibility instruments. Processing facilities include : high pass, low pass and periodic filters, spectrum and variance analysis, despiking, interpolation, edge matching, zero mean traverse correction, destagger correction, general purpose numeric functions (add, multiply, absolute, power, clip, compress, search and replace, randomise) and a powerful cut and combine function for combining data sets mathematically. Graphics may be presented as shade plots (grey scale or colour), trace plots (stacked profiles or 3D), dot- density or pattern plots and plotting parameters can be entered in standard, clip, compress or relief (artificial sun) mode. Appropriate combination of data processing and graphical display (e.g. specific tailoring of colour palette) may be used to enhance specific features.
Archaeological prospection is not done for scientific reasons alone, but it has also practical use for the creation of the record of archaeological sites. The first attempt for such a record was started in Bayern as early as 1880 covering the whole country. It was soon outdated and a second one was completed for one Regierungsbezirk (administration district) in 1909. For these and later attempts only visible monuments, e.g. barrows, hill forts etc. and stray finds were available. Therefore certain areas, for example the surroundings of Munich, where due to the geological situation stray finds are lacking, were regarded as being practically without any prehistoric settlements. This picture was completely changed with the introduction of aerial photography in the late 1970ies. Suddenly it became obvious that in this previous archaeological desert there were hundreds of settlements, graveyards and former barrows. Thanks to this information it was possible to conduct excavations before the sites were destroyed by building activities.
All local communities and other administrations are obliged to create land use and development control plans in which archaeological sites are included. Thanks to the results of aerial photography realistic information can now be given to the planning authorities. Still aerial photography has a big drawback: the absence of evidence on photos does not necessarily mean that there are no archaeological remains buried in the ground; a fact, which is often difficult to explain to investors and other people. It happens again and again that in places where aerial photography gives hardly any results, e.g. in the green land areas close to the Alps, that archaeological sites are discovered unexpectedly during construction activities.
Other prospection methods, e.g. magnetometer or georadar are seldom used before excavations, because it is cheaper to remove the top soil in the endangered area and see what has to be done, particularly if these services are conducted by contract archaeologists. But for the protection of sites under the Archäologische Reservate and the Grabungsschutzzonen scheme various prospection methods are used to gain knowledge about the character and extent of the monument. Phosphate analyses are seldom made, but in one case it was possible to link these results to different parts of Early Medieval houses.
To sum up: the management of cultural heritage would only be able to fulfil about one fifth of its tasks without any archaeological prospection.
The "Rheinisches Amt für Bodendenkmalpflege/Landschaftsverband Rheinland" (Bonn) often carries out archaeological prospections e.g. in the preliminary stages of development plans or ahead road construction. The first step is the analysis of the archive data like historical maps or the information about chance finds. The next step is systematic fieldwalking including single-find plotting. This method enables us, to date the site and to define its extend approximately. Fieldwalking is not applicable to meadows and does not yield reliable information about the preservation of the features. By means of a subsequent geophysical survey using magnetic and/or electric prospection on selected areas it is possible to locate different archaeological objects very precise. Based on the results of the geophysical survey well-aimed bore probes are carried out in order to prove the preservation. In difficult situations instead of bore probes you most likely use trial trenches.
To work successfully in archaeology in the open mining district of Cologne Basin it is necessary to get knowledge as far as possible of what you will see under the surface when digging into the ground.
This knowledge comes by archaeological prospection with the special science disciplines of geophysical measurements, geochemical proofs, geoarchaeological drillings, surface scans and last but not least aerial archaeology.
This remote sensing method since 1960 systematically at work in the 14400 km2 wide Rhineland area of Germany .
To focus this method specially in the three open-mine areas of the Cologne Basin a special project was set up running for over one year , financed by the Foundation „Stiftung Archäologie im Rheinischen Braunkohlenrevier". A main focus of this project was to test the abilities of vertical and oblique photos in connection with colour-infrared film material. This paper describes the project-aims, work and results illustrated with a few aerial photographs, plots and digital orthophotos of findings and brings out what changes in aerial archaeology in the whole Rhineland area are initiated by this project.
The following figures will illustrate the workflow from aerial archaeology findings to excavation of an Roman villa in the „Inden" mining district.
In a late Roman city wall of Celje in Slovenia there is, among other secondarily used stone material, a block with a Roman inscription. A part of an inscription is visible. The other part is hidden.
A preservation ethics indicates a non-destructive approach, used by the authors. To read a hidden part of an inscription we used electromagnetic (EM) modelling for Ground Penetrating Radar (GPR) imaging with a Finite Difference Time Domain modelling (FDTD).
The purpose of our experimental and modelling efforts is to achieve a pre-processed data base for 3D image reconstruction algorithm.
We present a rendering in three-dimensions with high resolution detail visualisation.