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Archaeological Prospection

Wiley Online Library : Archaeological Prospection

Published: 2017-07-01T00:00:00-05:00


Use of LIDAR and photointerpretation to map the water supply at the Las Murias-Los Tallares Roman gold mine (Castrocontrigo, León, Spain)


A comprehensive study of the water supply at Las Murias-Los Tallares Roman gold mine (Castrocontrigo, León, Spain) was conducted using LIDAR technology and photointerpretation that revealed all-new and interesting aspects both as concerns the length of the channels and their structure and supply capacity. Although LIDAR technology proves to be very valuable and essential to analysing Roman hydraulic mining structures, there are various limitations when reconstructing supply systems due to the accuracy of LIDAR data and the deterioration of the structures after having been abandoned for nearly 2,000 years.

Terrestrial laser scanning and photogrammetry techniques for documenting fossil-bearing palaeokarst with an example from the Drimolen Palaeocave System, South Africa


This paper presents the results of a recent three-dimensional (3D) survey at the Drimolen Makondo palaeontological deposits in the Hominid Sites of South Africa UNESCO World Heritage site. The Drimolen Makondo is a palaeokarstic feature that consists of a heavily eroded 2.6-2.0 Ma fossil-bearing palaeocave remnant. With photogrammetry and a laser scan survey, two 3D site models were created, georectified, and imported into geographical information system software. This paper outlines both of these survey techniques and provides an assessment of the relevant merits of each method and their applicability for detailed recording and archival documentation of palaeokarstic palaeontological and archaeological sites. Given the complex depositional context of many of the fossil-bearing South African cave systems and their importance for understanding our evolutionary history, new methods are critical to visualising and analysing 3D spatial data. The utility of 3D models lies in their ability to integrate with total station survey techniques to accurately record and control excavations and provide a means of visualising stratigraphic, sedimentary, and spatial contexts in various geographical information system platforms. The use of low-cost and time-efficient digital photographic surveys to create accurate 3D models, if completed accurately, can provide researchers with a means of contextualising excavation data without the need for expensive and highly specialised equipment. The development of this method combined with differential global positioning systems provides a solution in more remote locations to recording highly accurate fossil and 3D site contexts with increasing ease. It also allows the sites to be recorded as part of an evolving landscape rather than as single isolated localities. This technique should be a standard technique implemented when working on irreplaceable UNESCO World Heritage sites such as the hominin-bearing caves of South Africa.

Enhancing signals from buried Roman structures in Magnetometer data by combining continuous wavelet transform and tensor voting


In this paper, a processing chain is proposed for enhancing larger-scale building structures in magnetometer data using the continuous wavelet transform for extracting the horizontal location, depth, and homogeneity (or shape) of subsurface objects. Even though the values estimated from our data do not clearly describe the archaeological site, they are used as a filter step for removing objects whose depth and homogeneity fall outside a predefined range. This yields a binary map, where valid points represent the horizontal source positions of magnetic anomalies. In a second step, curvilinear subsets of points are identified on a larger scale by the tensor voting framework indicating archaeological relevant structures, such as arcs and lines. Here, a point casts votes on neighbouring points and their values depend on the distance, and relative position of the points. All votes are summed up and the final value discriminates, whether a certain point (and therefore a magnetic source) is part of a salient curve (e.g. arc, line). Thresholding removes points with lower values while keeping those with larger values. Although the result shows many geometric features, it still needs to be combined with other data, e.g. from aerial photography or excavations. In combination, the extracted features continue those structures in the aerial photograph, thus expanding the knowledge about the archaeological site.

The GPR investigation of the Shakespeare family graves


As part of a multi-disciplinary programme of archaeological investigation, GPR was used to investigate the Shakespeare family graves below the chancel of Holy Trinity Church in Stratford, Warwickshire, England. Although William Shakespeare's place as perhaps one of the most famous individuals who has ever lived has been cemented in the annals of history, much of his life and death is still shrouded in mystery. As a result, a large number of myths and legends have grown up around his burial place. These included the suggestion of an unusually deep burial or the presence of a large family crypt beneath the chancel floor. A series of multi-frequency surveys was carried out to establish the depth and structure of the graves and as much burial information as possible. Close survey (using a strategy developed and successfully applied in Westminster Abbey and other churches) was used in order to optimise the quality of patterning in the data. Within Holy Trinity, this strategy was validated by the detection of a known vault. The use of multiple frequencies was critical in this investigation in order both to detect the graves and also to establish information about the graves. Too low a frequency may result in non-detection because of the relatively low target resolution whereas too high a frequency risks insufficient depth penetration. From this process a number of myths can now be discounted, including the presence of a large Shakespeare family vault or crypt. Instead, the GPR survey suggests that a simple, shallow, earth-cut burial lies beneath William's tombstone. One story however concerning disturbance of William Shakespeare's grave in order to remove his skull does correspond with the evidence.

Geoarchaeological evaluation of ground penetrating radar and magnetometry surveys at the Iron Age burial mound Rom in Norway


Following magnetometry and ground penetrating radar surveys, a geoarchaeological field evaluation was carried out at the Iron Age burial mound of Rom in Slagendalen, Vestfold County, Norway, in order to assess the accuracy of the geophysical data interpretation and to investigate specific questions that have arisen during data interpretation. The evaluation was conducted within the framework of an archaeological excavation campaign in 2013, which enabled direct access to the subsurface materials. The archaeological stratification was recorded by laser scanning using a three-dimensional (3D) single-surface approach, permitting a virtual reconstruction of the excavated part of the mound and facilitating the comparison between excavation and prospection data. Selected sediment sequences were targeted with in situ and laboratory-based measurements for correlation purposes, including magnetic susceptibility, electrical conductivity and water content measurements. Here we present the methodological approach and the results of the geophysical prospection surveys, followed by a geoarchaeological evaluation and a discussion of the impact on the overall archaeological investigation.

A pixel-based semi-stochastic algorithm for the registration of geophysical images


The availability of overlapping geophysical data produced by different sensors provides complementary information about the investigation area. However, joint interpretation of these geophysical images is challenging. One common problem is the registration of the images that is necessary to compare features appearing in dissimilar datasets. Measurements in archeological geophysics are often performed by handheld devices therefore, the actual location of the measurement could be different from the planned one. These offsets are localized and essentially random. Consequently, it is impossible to correct them following usual deterministic approaches. This paper presents a novel registration method between geophysical images produced from different prospecting methods. We developed a semi-stochastic, iterative registration algorithm that applies random local transformations in small randomly selected regions of the processed image. The algorithm uses the mutual information of the images as similarity measure due to its suitability in images of different modalities. We use a pair of images to train the algorithm and tune its parameters. Afterwards, we test the method with nine different pairs of geophysical images from various locations and characteristics. The results, in all cases, show a significant increase of the mutual information in comparison with the registration through geographical coordinates.

Large-scale geophysical archaeological prospection pilot study at Viking Age and medieval sites in west Jutland, Denmark


In 2014, a team of the Ludwig Boltzmann Institute for Archaeological Prospection and Virtual Archaeology, in collaboration with Holstebro Museum, conducted a geophysical archaeological prospection pilot study at several Viking Age and medieval sites in West Jutland, Denmark; sites that had been discovered earlier by aerial archaeology. The high-resolution surveys employed motorized ground-penetrating radar (GPR) and magnetometer systems as well as novel post-processing software. The aim of this study was to test the suitability of these methods and the chosen approach to efficiently explore, investigate and document prehistoric settlements on a large scale under the prevalent environmental conditions in this part of Denmark. Over the course of five days of fieldwork, numerous structures of archaeological interest, such as the remains of longhouses, property boundaries, pathways, pit houses and other buried remains of the settlements, were detected and mapped. The combination of the data gathered by magnetic and GPR prospection with the already existing aerial imagery permitted an integrated archaeological interpretation, resulting in considerable new knowledge about the investigated sites. In this paper, we present the results obtained for the Viking Age settlement at Stadil Mølleby and a medieval village near Rysensten, both situated on sandy soils.

Removal of sensor tilt noise in fluxgate gradiometer survey data by applying one-dimensional wavelet filtering


Archaeological prospection with magnetometer instruments is performed in a wide range of field configurations, ranging from single probe setups to mobile arrays that allow combining multiple sensors. The latter type, whereby instruments are mounted onto a cart system, are particularly prone to motion-induced noise. Sensor tilt, for example, causes in-line noise that can obscure magnetic variations present. To remediate these effects, image processing techniques are the most frequently applied. However, while efficient in producing more levelled data plots, these procedures are often associated with a smoothing penalty whereby low-intensity or small-scale anomalies are masked. We propose a one-dimensional signal processing approach, based on discrete wavelet analysis. By selecting wavelets that correspond to the motion-induced noise patterns, such effects can be targeted more precisely, reducing the risk of feature masking or artefact creation. Evaluation of the proposed procedure on three fluxgate gradiometer datasets collected with a hand-propelled push-cart system, proved it a valid and more dedicated method to reduce the impact of motion induced noise in magnetometry data collected with cart mounted array setups.

Geochemical insight during archaeological geophysical exploration through in situ X-ray fluorescence spectrometry


Geophysical techniques are widely applied in archaeological exploration, providing rapid and non-invasive site appraisal. Geochemical analyses contribute significantly in archaeometry, but conventional laboratory apparatus requires that samples are removed from their in situ context. Recent advances in field-portable apparatus facilitate in situ geochemical analysis, and this apparatus is deployed in this paper alongside conventional geophysical analysis to characterize the archaeological prospectivity of a site. The target is subsurface debris at the crash site of a World War II Mosquito aircraft. A 100 m long transect of magnetic, electromagnetic (EM) and in situ X-ray fluorescence (XRF) measurements was acquired in November 2014, with soil samples also collected for laboratory validation. A subset of XRF measurements was repeated in August 2015 alongside a targeted grid, 900 m2 in area, of magnetic gradiometry profiles. Built chiefly from wood, the Mosquito responds weakly in magnetic and EM data; magnetic gradient anomalies of ±10 nT/m are instead attributed to thermoremanence in a burnt layer at 0.2–0.4 m depth, produced by the impact fire following the crash. XRF spectrometry reveals co-located enrichments in copper (Cu) and zinc (Zn) ions (400% and 200%, respectively, above background). These metals are alloyed into brass, present in abundance in the ammunition on board the Mosquito. Records from the in situ XRF sampling compare well with laboratory validated data, although a bespoke calibration for the local soil type would improve the reliability of absolute geochemical concentrations. XRF responses vary significantly with ground conditions: the November 2014 acquisition was performed soon after ploughing at the site, potentially providing a fresh charge of metallic contaminants to the ground surface. Where the chemistry of a target is anomalous with respect to host soil and a source-to-surface transport mechanism is present, in situ XRF analysis offers improved understanding of a target compared to geophysical interpretation alone.

LiDAR-guided Archaeological Survey of a Mediterranean Landscape: Lessons from the Ancient Greek Polis of Kolophon (Ionia, Western Anatolia)


In 2013, an airborne laser scan survey was conducted in the territory of the Ionian city of Kolophon near the western coast of modern Turkey as part of an archaeological survey project carried out by the Mimar Sinan University of Istanbul (Turkey) and the University of Vienna (Austria). Several light detection and ranging (LiDAR) studies have been carried out in the temperate climate zones of Europe, but only a few in Mediterranean landscapes. Our study is based on the first LiDAR survey carried out for an archaeological purpose in Turkey and one of the first in the Mediterranean that have been planned, measured and filtered especially for archaeological research questions. The interpretation of LiDAR data combined with ground-observations proved extremely useful for the detection and documentation of archaeological remains below Mediterranean evergreen vegetation and dense maquis. This article deals with the methodological aspects of interpreting LiDAR data, using the Kolophon data as a case study. We offer a discussion of the strengths and limitations of LiDAR as an archaeological remote sensing method and suggest a best practice model for interpreting LiDAR data in a Mediterranean context. © 2017 The Authors. Archaeological Prospection published by John Wiley & Sons Ltd.

Reconstruction of a Palaeosurface and Archaeological Site Location in an Anthropogenic Drift Sand Area


Knowledge of the position of archaeological remains in the surface relief provides important basic information for archaeological survey design and interpretation. Geomorphological processes in (pre)history may have resulted in a modification of the local relief around archaeological sites, especially in areas that are prone to sediment erosion and relocation, such as sheet sand and dune landscapes. In this study, we reconstructed and analysed the palaeorelief of an archaeological excavation site in an inland dune area in southern Brandenburg, Germany. The remains of two Mesolithic sites were documented in the archaeological excavations and found to be associated with a buried soil horizon. To gather information on the relief of the buried soil surface, we used a combination of sedimentological and pedological profile descriptions along archaeological survey trenches and geophysical prospection with ground penetrating radar supplemented with microdrone photography and photogrammetry, global positioning system (GPS) surveys, and analysis of LiDAR-based elevation models. A digital elevation model of the buried surface was generated and analysed using a geographical information system (GIS). A comparison of the palaeosurface model with the recent surface elevation model shows that sand remobilization resulted in a considerable reshaping of the relief. Further, an analysis of the buried surface model shows that the relief position of the two archaeological sites in the study area was considerably more prominent in relation to the corresponding buried soil surface than in relation to the recent surface morphology. The results affirm the significance of Holocene sediment relocation for the local surface morphology and the importance of considering such relief modifications in archaeological surveys. Copyright © 2017 John Wiley & Sons, Ltd.

Drones in Archaeology. State-of-the-art and Future Perspectives


In addition to traditional platforms for low-level remote sensing (balloons, kites, etc.) new and more complex automated systems [unmanned aerial vehicles (UAVs) or drones] have become available in the last decade. The success and market expansion of these platforms has been a driving force in the development of active and passive sensors specifically designed for UAVs. In the last few years archaeologists have started testing both platforms and sensors, particularly for the following applications: three-dimensional (3D) documentation of archaeological excavations; 3D survey of monuments and historic buildings; survey of archaeological sites and landscapes; exploratory aerial survey; and the archaeological survey of woodland areas. The scale of these applications has ranged from site-based to landscapes-based (approximately up to about 10 km2 in extent). The role of such platforms in the archaeological survey of excavations and landscapes, and in diagnostics more generally, is of great interest and is inexorably growing. Copyright © 2017 John Wiley & Sons, Ltd.

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No abstract is available for this article.

2D-ERT Survey for the Identification of Archaeological and Historical Structures beneath the Plaza of Santo Domingo, Mexico City, Mexico


Santo Domingo public square (Plaza of Santo Domingo) is located in Mexico City's downtown area. The history of its transformations began in pre-Hispanic times and is still being written. The objectives of this investigation were to establish the position of the northwest corner of the ancient Mexica wall and to determine whether the Plaza became a public square during pre-Hispanic or colonial times, taking into account the contradictions of the historical sources. For this purpose, we implemented three 80-m-long electrical resistivity tomography (ERT) profiles in the Plaza and one on the eastern side of the Church of Santo Domingo de Guzmán. A Wenner–Schulmberger array was designed for the data acquisition. The results could support the hypothesis that the Plaza of Santo Domingo was designed and constructed as an open public area in colonial times, since the observations in the electric profiles beneath the square could reveal the presence of a pre-Hispanic structure. This structure could be part of the wall that surrounded the Mexica ceremonial compound. At the eastern side of the Dominican church, the foundations of the first Spanish chapel were identified, as well as portions of modern concrete deposits injected into the subsoil to stabilize the constant subsidence of the building. Copyright © 2016 John Wiley & Sons, Ltd.

Simulating Trial Trenches for Archaeological Prospection: Assessing the Variability in Intersection Rates


In this study we draw attention to the inherent variability in the results of trial trenching, when taking into account the countless variations in orientation and positioning of trenches. Grids of trial trenches were simulated time and again on the excavation plans of 16 archaeological sites from Flanders, Belgium. Orientation and positioning of the grid layout was shifted randomly, whilst the area coverage varied from 2.5% to 80%. The intersection rates of the archaeological features allow to gain more insight in trends and variability that are inherent to the chosen design of trial trenches. It is assessed how robust a chosen grid layout performs on (multi-period) archaeological sites and how variable these results might be. The most effective layout appears to be a grid with short, parallel and discontinuous trenches or a standard grid, closely followed by 2 m wide continuous trenches. Implementing 4 m wide trenches reduces the effectiveness of the latter method substantially. When the area coverage of the trenches is below 10%, the results of the archaeological prospection become unreliable and can potentially lead to a substantial over-or underestimation of the actual feature density on the site. Copyright © 2016 John Wiley & Sons, Ltd.

Object-based Shell Craters Classification from LiDAR-derived Sky-view Factor


This paper presents the results of the first attempt to assess, identify and quantify the residual number of shell craters of World War I currently present in the Vezzena/Luserna/Lavarone Plateau, areas of Millegrobbe, Bisele and Cima Campo (Province of Trento, Italy). Historical sources report the existence of several thousand artillery explosions: therefore, a field survey or a classic photo-interpretation would be labour-intensive and highly time-consuming. For this reason, a digital terrain model (DTM) of the test-site was processed using the Sky-view Factor algorithm and was analysed with an object-based approach, which implied: (1) multiresolution segmentation; (2) classification (main features considered size, shape and colour). The automatically classified shell craters were thus verified during an in situ survey that determined the accuracy of the method in the order of 84% of the total occurrences. Copyright © 2016 John Wiley & Sons, Ltd.

Geochemical Survey and Evaluation Excavations at Alderley Edge: Recognizing Anthropogenic Signatures within a Mining Site-scape


Archaeological science and field investigations are making greater use of multi-element geochemical survey as a tool for site prospection and intra-excavation analysis. This increasing use of geochemical survey is allowing a new field of geoprospection to develop, a technique that has specific relevance to the investigation of sites containing archaeometallurgical evidence, due to the high geochemical loadings within archaeological contexts produced from past metalworking activities. Correspondingly, there have been relatively few published examples that compare the results of geochemical surveys against excavation data. This study reports the use of geochemical data to investigate a multi-period mining site-scape at Alderley Edge, Cheshire, UK. The geochemical data is analysed using principle component analysis, which facilitates the identification of a number of geochemical anomalies. The site taphonomy and stratigraphic evolution of this mining site-scape is complex, with naturally occurring areas of lead and copper mineralization and a history of exploitation since the early Bronze Age. The geochemical anomalies were compared to the results of excavation within the survey area and this combination of excavation and prospection data allowed the reasons for the different geochemical anomalies to be explained. The article highlights the potential of using multi-element geochemical survey to investigate sites containing archaeometallurgical remains and provides a discussion of why context specificity is essential to correctly interpret multi-element geochemical data. Copyright © 2017 John Wiley & Sons, Ltd.

The Passive Seismic Technique ‘HVSR’ as a Reconnaissance Tool for Mapping Paleo-soils: The Case of the Pilastri Archaeological Site, Northern Italy


Horizontal-to-vertical spectral ratio (HVSR) is a widely used geophysical technique in seismic microzonation studies. It is based on a specific analysis of seismic ambient noise. The method allows to obtain the frequency and amplitude of the resonance peaks of a layered earth with increasing acoustic impedance contrasts. The peaks can be interpreted to obtain an estimation of depth(s) of the impedance contrast horizon(s). Based on the assumption that long-term human trampling results in sediment's stiffening, which increased both density and velocity of seismic shear waves, the HVSR method was applied to investigate the shallow subsurface of an important, Middle Bronze Age, archaeological site called ‘Pilastri Terramara’ discovered at the end of the last century. Following recent excavations, archaeologists supposed that the settlement could extend outside the initially hypothesized borders, and decided to involve geophysicists to verify the truthiness of this new hypothesis and consequently to map the possible spatial extent of the paleo-surfaces frequented by ancient occupants. The purpose of the geophysical investigation was then to detect and possibly to map one or more anthropogenic paleo-surfaces over a relatively large area (about 12000 m2). Unfortunately, direct evidences showed that the paleo-surfaces were embedded in clayey sediments and laying at depths ranging between 50 and 170 cm below ground level. Furthermore, the area to be investigated is occupied by a farm with glasshouses and other buildings. These obstacles constituted a real challenge that hindered the utilization of the most commonly used geophysical methods in archaeology, i.e. ground penetration radar (GPR), magnetometry and electrical resistivity tomography. For these reasons, we decided to use the HVSR method as a reconnaissance exploration tool, to confirm or rule out the presence of such paleo-surfaces. Spectral peaks related to acoustic horizons provided evidences about their presence and allowed to estimate their depths as was later confirmed by a new excavation. Copyright © 2017 John Wiley & Sons, Ltd.

Reconstructing Palaeogeography and Inter-island Visibility in the Wallacean Archipelago During the Likely Period of Sahul Colonization, 65–45 000 Years Ago


The palaeogeography of the Wallacea Archipelago is a significant factor in understanding early modern human colonization of Sahul (Australia and New Guinea), and models of colonization patterns, as well as archaeological survey and site interpretation, are all heavily dependent on the specific palaeogeographic reconstruction employed. Here we present five reconstructions for the periods 65, 60, 55, 50, and 45 000 years ago, using the latest bathometric chart and a sea-level model that is adjusted to account for the average uplift rate known from Wallacea. Using this data we also reconstructed island areal extent as well as topography for each time period. These reconstructions were then used to estimate visibility for each island in the archipelago, and finally to model how intervisible each island was during the period of likely human colonization. Our models provide the first evidence for intervisibility between Timor and Australia at ca. 65–62 ka and 47–12 ka, the second of which is notable for its overlap with the oldest radiocarbon dates from Timor-Leste and Australia. Based on intervisibility alone, however, our study suggests that the northern route into Papua New Guinea was the most parsimonious route for first modern human entry into Sahul. Our study provides archaeologists with an important baseline from which to conduct physical surveys, interpret archaeological data, and theorize the colonization of Wallacea and Sahul. © 2017 The Authors. Archaeological Prospection Published by John Wiley & Sons Ltd.