Ammaia is situated about 10 km west of the border between Portugal and Spain, south of the villag... more Ammaia is situated about 10 km west of the border between Portugal and Spain, south of the village of São Salvador da Aramenha (district of Portalegre). Except for a few farms, the site has remained virtually undisturbed by modern construction. Since 1994, excavations undertaken by the Fundacão Cidade de Ammaia and the universities of Évora and Coimbra, have focused mainly on areas marked by extant structures, such as the forum and the southern gate. Since April 2009, the Radio-Past project (www.radiopast.eu) combines different geophysical and other prospection techniques to map the entire area of the Roman town and its surroundings.
Vermeulen, F., Dapper, M. de, Mušič, B., Monsieur, P., Verreyke, H., Carboni, F., Dralans, S., Ve... more Vermeulen, F., Dapper, M. de, Mušič, B., Monsieur, P., Verreyke, H., Carboni, F., Dralans, S., Verhoeven, G.J.J., Verdonck, L., Hay, S., Sterry, M., Paepe, P. de, Seranno, S. de, 2009. Investigating the Impact of Roman Urbanisation on the Landscape of the Potenza Valley. BABesch - Bulletin Antieke Beschaving 84 (0), 85–110.
This paper presents the results of a GPR survey carried out at the Roman town of Mariana (Corsica... more This paper presents the results of a GPR survey carried out at the Roman town of Mariana (Corsica, France). Excavations (1959-1965 and 2000-2007) yielded a Roman street with houses and shops, an early mediaeval cathedral and a mediaeval bishop's palace. When compared with the hypothetical town limits derived from aerial photography, old cadastral maps and the location of two cemeteries, the excavations are in an eccentric position. The principal aim of the geophysical survey was to shed more light on the Early Imperial town centre (1 st-2 nd century AD), which was to be found further north. The results from a fluxgate gradiometer survey demonstrated the presence of buildings with an orientation corresponding to the excavated street. In the GPR data, an orthogonal street system became noticeable and most of the buildings can be identified as private dwellings. In several parts of the town, there are indications for more than one occupation phase. For example, in the northwestern insula of the main survey area, the GPR results show a large building complex with deep foundations, as well as shallow walls of poor construction quality in the courtyard of this building. A trial excavation confirmed this dichotomy: it revealed solid walls with brick facings originating in the 1 st or 2 nd century AD, as opposed to alignments of loose boulders, not older than the 3rd century. On the basis of the GPR results, two small excavation trenches from the 1930s, one of which contained the remains of a bathhouse, can now be located exactly. tury BC. Shortly after 100 BC, Alalia was rebuilt and renamed Aleria and became the economic capital with a monumental city infrastructure and an important naval base. At the same time, another city, Mariana, was built at the mouth of the river Golo. Together with the capital this town became the driving force behind the integration of the island and its inhabitants into the Roman civilization (Vismara 2005). Although Corsica would become a place of exile for political opponents in Rome and some exports of silver and iron are known, the island remained a relatively isolated region of the western Roman Empire until the invasion by the Vandals in AD 436. Its rugged landscape was not well suited to major agricultural pursuits and a major part of its indigenous inhabitants were relatively closed to the outside world (Pergola 2004). Nevertheless, current archaeological research in and around the city of Mariana demonstrates the important imprint of the Roman society on the island between the 1st century BC and the 5th century AD. Thanks to Seneca, who was exiled in Corsica, we know that Mariana was a colonia civium Romanorum, a colony of Roman citizens (Seneca, De Consolatione ad Helviam Matrem, VIII, 8) and that it took its name from the founder, Gaius Marius. Although archaeological proof for the first dec
ABSTRACT This paper presents a ground-penetrating radar (GPR) survey over two circular structures... more ABSTRACT This paper presents a ground-penetrating radar (GPR) survey over two circular structures originally surrounding Bronze Age burial mounds at the site of Koekelare (western Belgium). The region is characterized by sandy soils. Their low water storage capacity and the ...
Our understanding of Roman urbanism relies on evidence from a few extensively investigated sites,... more Our understanding of Roman urbanism relies on evidence from a few extensively investigated sites, such as Pompeii and Ostia, which are unrepresentative of the full variety of Roman towns. This article presents the results of the first high-resolution GPR survey of a complete Roman town-Falerii Novi, in Lazio, Italy. The authors review the methods deployed and provide an overview of the results, including discussion of a case-study area within the town. They demonstrate how this type of survey has the potential to revolutionise archaeological studies of urban sites, while also challenging current methods of analysing and publishing large-scale GPR datasets.
Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna element... more Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna elements in a fixed configuration has become more common. The investment needed for these systems is significant. In order to reduce the recording time in the field, an alternative is the use of several single GPR antennas in parallel (a 'modular system'). Although this does not match the fast acquisition of detailed data sets by means of multi-channel arrays, a system consisting in single antennas can gradually be expanded and investment can be spread over time. This paper presents a 2D and a full-resolution 3D survey, conducted with a modular GPR instrument. A characteristic of these systems is that the cross-line separation between transmitter-receiver pairs is larger than the sampling distance prescribed by the Nyquist theorem. As a consequence, for 3D data collection, profiles have to be acquired between previously recorded ones, which requires high positioning accuracy. A completely identical response for different single GPR antennas is difficult to achieve. For the system tested, on less favourable soils this resulted in striping in the horizontal slices. Several methods (3D frequency-wavenumber filtering, eigenimage filtering, mean profile filtering and filtering based on discrete wavelet transform, discrete ridgelet transform and linear Radon transform) were applied to two data sets exhibiting different kinds of linear noise and their capability to suppress artefacts was assessed. Although overall a reduction of the stripe patterns was achieved, mostly it was impossible to fully eliminate the noise in the time-slices without low-pass filtering in the cross-line direction. For the 2D data, low-pass filtering caused loss of some of the archaeological response and therefore was not applied. Mean profile filtering allowed the most reliable characterization of the archaeological structures. When the available resources do not allow the high levels of investment demanded by large multi-channel systems, an obvious alternative to reduce the field time is the use of several independent single antennas in parallel (Leckebusch 2005). Such a 'modular system' does not equal the combined acquisition speed and dense sampling of multi-channel GPR systems. On the other hand, a modular system can gradually be expanded and investment can be spread over time. Furthermore, large multi-channel arrays can be difficult to operate in restricted spaces (e.g., Linford et al. 2011) and on fields with a rough surface or otherwise inaccessible for systems towed behind a vehicle (e.g., Utsi 2010; Seren et al. 2011). This paper presents a 2D and a fullresolution 3D survey with a pulsed modular GPR system. The requirements with regard to positioning are indicated, examples of existing filtering procedures to suppress stripes along the survey lines are shown and their effectiveness compared.
Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna element... more Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna elements in a fixed configuration has become more common. The investment needed for these systems is significant. Although gradually expandable modular systems, ...
and the Superintendence of Cultural Heritage (Malta) since 2008. It is an intensive systematic fi... more and the Superintendence of Cultural Heritage (Malta) since 2008. It is an intensive systematic field-walking survey in a kilometre-wide transect, beyond the main Phoenician and Punic urban centre on the island, the present-day Rabat/Mdina. It is interdisciplinary, involving not only archaeologists, but also ceramic specialists, geophysicists, geomatic specialists/topographers and geomorphologists. Three permanently inhabited sites were encountered dating to at least the late 6th or early 5th century BCE, with a clearer attestation in the Hellenistic/Roman period and Late Antique periods. The resulting reconstructed settlement pattern of the Phoenician/Punic period suggests a managed landscape that seems to be a good reflexion of what is happening in North Africa and elsewhere in the central and western Mediterranean. At least from the Roman period on, these sites seem to have specialised on the production of olive oil. The poster presentation focuses upon the major site in the survey transect, the Ġebel Għawżara site.
This study aimed to evaluate the different configurations of an electromagnetic induction (EMI) s... more This study aimed to evaluate the different configurations of an electromagnetic induction (EMI) sensor, the EM38DD (Geonics Limited, Canada) with fluxgate gradiometer measurements on an archaeological site. The EM38DD allows measuring both the apparent magnetic susceptibility (MSa or χa) and the apparent electrical conductivity (ECa or σa) in two different coil orientations. A gradiometer measures the lateral variations of the vertical magnetic field gradient, caused by the induced and remanent magnetisations. An archaeological site where historical documents indicated the presence of a 17th century brick castle was selected as a test area. The results of the first survey with the EM38DD showed very strong magnetic anomalies in the central field, which were caused by the brick remains of the castle. Therefore, a smaller area was chosen within this field to compare the different configurations of the EM38DD with the gradiometer at the same measurement resolution. The most useful resu...
ABSTRACT Ground Penetrating Radar (GPR) reflections occur at sharp interfaces between contrasting... more ABSTRACT Ground Penetrating Radar (GPR) reflections occur at sharp interfaces between contrasting soil layers. Generally, the depth of the interface is expressed as the two-way travel time from the transmitting to the receiving antenna. Converting these travel times to depths requires knowledge of the propagation speed of the GPR wave in the soil.This velocity is influenced by the electric properties of the soil water content, mainly by the dielectric permittivity (ε). The soil electrical conductivity (σ), which also depends on the soil water content, can be accounted for by electromagnetic (EMI) induction prospecting. A procedure was proposed to thoroughly characterize a circular ditch system by inverting the apparent electrical conductivity (σa) measurements from a multi-receiver EMI instrument based on GPR profile data. A fitting procedure allowed to calibrate both the propagation speed of the GPR waves up to the interface between the ditch infilling and the underlying sand and the conductivities of both layers. Integrating the simultaneous EMI measurements and high-resolution GPR depth profiles and –slices improved the non-invasive dimensioning of the circular ditch system.
Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna element... more Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna elements in a fixed configuration has become more common. The investment needed for these systems is significant. Although gradually expandable modular systems, consisting of antennas which can be used independently, do not match the fast acquisition of detailed datasets by means of multi-channel arrays, they can help finding a compromise between increased acquisition speed and (limited) resources. In modular systems, the separation between transmitter-receiver pairs is often larger than the sampling distance prescribed by the Nyquist theorem. As a consequence, additional profiles have to be recorded in between, which requires a high positioning precision. As a completely identical response for the different antennas in an array is difficult to achieve, stripes can occur in the horizontal slices, especially when ringing occurs. This complicates the interpretation of features in the direction of the survey lines. In this paper, a three dimensional frequency-wavenumber filter is proposed, consisting in a combination of a circular filter and a fan filter. The application of this filter to GPR data collected at the Roman town Mariana (Corsica, France) showed a reduction of the stripe patterns, allowing a more reliable characterization of subtle archaeological structures.
Ammaia is situated about 10 km west of the border between Portugal and Spain, south of the villag... more Ammaia is situated about 10 km west of the border between Portugal and Spain, south of the village of São Salvador da Aramenha (district of Portalegre). Except for a few farms, the site has remained virtually undisturbed by modern construction. Since 1994, excavations undertaken by the Fundacão Cidade de Ammaia and the universities of Évora and Coimbra, have focused mainly on areas marked by extant structures, such as the forum and the southern gate. Since April 2009, the Radio-Past project (www.radiopast.eu) combines different geophysical and other prospection techniques to map the entire area of the Roman town and its surroundings.
Vermeulen, F., Dapper, M. de, Mušič, B., Monsieur, P., Verreyke, H., Carboni, F., Dralans, S., Ve... more Vermeulen, F., Dapper, M. de, Mušič, B., Monsieur, P., Verreyke, H., Carboni, F., Dralans, S., Verhoeven, G.J.J., Verdonck, L., Hay, S., Sterry, M., Paepe, P. de, Seranno, S. de, 2009. Investigating the Impact of Roman Urbanisation on the Landscape of the Potenza Valley. BABesch - Bulletin Antieke Beschaving 84 (0), 85–110.
This paper presents the results of a GPR survey carried out at the Roman town of Mariana (Corsica... more This paper presents the results of a GPR survey carried out at the Roman town of Mariana (Corsica, France). Excavations (1959-1965 and 2000-2007) yielded a Roman street with houses and shops, an early mediaeval cathedral and a mediaeval bishop's palace. When compared with the hypothetical town limits derived from aerial photography, old cadastral maps and the location of two cemeteries, the excavations are in an eccentric position. The principal aim of the geophysical survey was to shed more light on the Early Imperial town centre (1 st-2 nd century AD), which was to be found further north. The results from a fluxgate gradiometer survey demonstrated the presence of buildings with an orientation corresponding to the excavated street. In the GPR data, an orthogonal street system became noticeable and most of the buildings can be identified as private dwellings. In several parts of the town, there are indications for more than one occupation phase. For example, in the northwestern insula of the main survey area, the GPR results show a large building complex with deep foundations, as well as shallow walls of poor construction quality in the courtyard of this building. A trial excavation confirmed this dichotomy: it revealed solid walls with brick facings originating in the 1 st or 2 nd century AD, as opposed to alignments of loose boulders, not older than the 3rd century. On the basis of the GPR results, two small excavation trenches from the 1930s, one of which contained the remains of a bathhouse, can now be located exactly. tury BC. Shortly after 100 BC, Alalia was rebuilt and renamed Aleria and became the economic capital with a monumental city infrastructure and an important naval base. At the same time, another city, Mariana, was built at the mouth of the river Golo. Together with the capital this town became the driving force behind the integration of the island and its inhabitants into the Roman civilization (Vismara 2005). Although Corsica would become a place of exile for political opponents in Rome and some exports of silver and iron are known, the island remained a relatively isolated region of the western Roman Empire until the invasion by the Vandals in AD 436. Its rugged landscape was not well suited to major agricultural pursuits and a major part of its indigenous inhabitants were relatively closed to the outside world (Pergola 2004). Nevertheless, current archaeological research in and around the city of Mariana demonstrates the important imprint of the Roman society on the island between the 1st century BC and the 5th century AD. Thanks to Seneca, who was exiled in Corsica, we know that Mariana was a colonia civium Romanorum, a colony of Roman citizens (Seneca, De Consolatione ad Helviam Matrem, VIII, 8) and that it took its name from the founder, Gaius Marius. Although archaeological proof for the first dec
ABSTRACT This paper presents a ground-penetrating radar (GPR) survey over two circular structures... more ABSTRACT This paper presents a ground-penetrating radar (GPR) survey over two circular structures originally surrounding Bronze Age burial mounds at the site of Koekelare (western Belgium). The region is characterized by sandy soils. Their low water storage capacity and the ...
Our understanding of Roman urbanism relies on evidence from a few extensively investigated sites,... more Our understanding of Roman urbanism relies on evidence from a few extensively investigated sites, such as Pompeii and Ostia, which are unrepresentative of the full variety of Roman towns. This article presents the results of the first high-resolution GPR survey of a complete Roman town-Falerii Novi, in Lazio, Italy. The authors review the methods deployed and provide an overview of the results, including discussion of a case-study area within the town. They demonstrate how this type of survey has the potential to revolutionise archaeological studies of urban sites, while also challenging current methods of analysing and publishing large-scale GPR datasets.
Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna element... more Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna elements in a fixed configuration has become more common. The investment needed for these systems is significant. In order to reduce the recording time in the field, an alternative is the use of several single GPR antennas in parallel (a 'modular system'). Although this does not match the fast acquisition of detailed data sets by means of multi-channel arrays, a system consisting in single antennas can gradually be expanded and investment can be spread over time. This paper presents a 2D and a full-resolution 3D survey, conducted with a modular GPR instrument. A characteristic of these systems is that the cross-line separation between transmitter-receiver pairs is larger than the sampling distance prescribed by the Nyquist theorem. As a consequence, for 3D data collection, profiles have to be acquired between previously recorded ones, which requires high positioning accuracy. A completely identical response for different single GPR antennas is difficult to achieve. For the system tested, on less favourable soils this resulted in striping in the horizontal slices. Several methods (3D frequency-wavenumber filtering, eigenimage filtering, mean profile filtering and filtering based on discrete wavelet transform, discrete ridgelet transform and linear Radon transform) were applied to two data sets exhibiting different kinds of linear noise and their capability to suppress artefacts was assessed. Although overall a reduction of the stripe patterns was achieved, mostly it was impossible to fully eliminate the noise in the time-slices without low-pass filtering in the cross-line direction. For the 2D data, low-pass filtering caused loss of some of the archaeological response and therefore was not applied. Mean profile filtering allowed the most reliable characterization of the archaeological structures. When the available resources do not allow the high levels of investment demanded by large multi-channel systems, an obvious alternative to reduce the field time is the use of several independent single antennas in parallel (Leckebusch 2005). Such a 'modular system' does not equal the combined acquisition speed and dense sampling of multi-channel GPR systems. On the other hand, a modular system can gradually be expanded and investment can be spread over time. Furthermore, large multi-channel arrays can be difficult to operate in restricted spaces (e.g., Linford et al. 2011) and on fields with a rough surface or otherwise inaccessible for systems towed behind a vehicle (e.g., Utsi 2010; Seren et al. 2011). This paper presents a 2D and a fullresolution 3D survey with a pulsed modular GPR system. The requirements with regard to positioning are indicated, examples of existing filtering procedures to suppress stripes along the survey lines are shown and their effectiveness compared.
Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna element... more Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna elements in a fixed configuration has become more common. The investment needed for these systems is significant. Although gradually expandable modular systems, ...
and the Superintendence of Cultural Heritage (Malta) since 2008. It is an intensive systematic fi... more and the Superintendence of Cultural Heritage (Malta) since 2008. It is an intensive systematic field-walking survey in a kilometre-wide transect, beyond the main Phoenician and Punic urban centre on the island, the present-day Rabat/Mdina. It is interdisciplinary, involving not only archaeologists, but also ceramic specialists, geophysicists, geomatic specialists/topographers and geomorphologists. Three permanently inhabited sites were encountered dating to at least the late 6th or early 5th century BCE, with a clearer attestation in the Hellenistic/Roman period and Late Antique periods. The resulting reconstructed settlement pattern of the Phoenician/Punic period suggests a managed landscape that seems to be a good reflexion of what is happening in North Africa and elsewhere in the central and western Mediterranean. At least from the Roman period on, these sites seem to have specialised on the production of olive oil. The poster presentation focuses upon the major site in the survey transect, the Ġebel Għawżara site.
This study aimed to evaluate the different configurations of an electromagnetic induction (EMI) s... more This study aimed to evaluate the different configurations of an electromagnetic induction (EMI) sensor, the EM38DD (Geonics Limited, Canada) with fluxgate gradiometer measurements on an archaeological site. The EM38DD allows measuring both the apparent magnetic susceptibility (MSa or χa) and the apparent electrical conductivity (ECa or σa) in two different coil orientations. A gradiometer measures the lateral variations of the vertical magnetic field gradient, caused by the induced and remanent magnetisations. An archaeological site where historical documents indicated the presence of a 17th century brick castle was selected as a test area. The results of the first survey with the EM38DD showed very strong magnetic anomalies in the central field, which were caused by the brick remains of the castle. Therefore, a smaller area was chosen within this field to compare the different configurations of the EM38DD with the gradiometer at the same measurement resolution. The most useful resu...
ABSTRACT Ground Penetrating Radar (GPR) reflections occur at sharp interfaces between contrasting... more ABSTRACT Ground Penetrating Radar (GPR) reflections occur at sharp interfaces between contrasting soil layers. Generally, the depth of the interface is expressed as the two-way travel time from the transmitting to the receiving antenna. Converting these travel times to depths requires knowledge of the propagation speed of the GPR wave in the soil.This velocity is influenced by the electric properties of the soil water content, mainly by the dielectric permittivity (ε). The soil electrical conductivity (σ), which also depends on the soil water content, can be accounted for by electromagnetic (EMI) induction prospecting. A procedure was proposed to thoroughly characterize a circular ditch system by inverting the apparent electrical conductivity (σa) measurements from a multi-receiver EMI instrument based on GPR profile data. A fitting procedure allowed to calibrate both the propagation speed of the GPR waves up to the interface between the ditch infilling and the underlying sand and the conductivities of both layers. Integrating the simultaneous EMI measurements and high-resolution GPR depth profiles and –slices improved the non-invasive dimensioning of the circular ditch system.
Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna element... more Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna elements in a fixed configuration has become more common. The investment needed for these systems is significant. Although gradually expandable modular systems, consisting of antennas which can be used independently, do not match the fast acquisition of detailed datasets by means of multi-channel arrays, they can help finding a compromise between increased acquisition speed and (limited) resources. In modular systems, the separation between transmitter-receiver pairs is often larger than the sampling distance prescribed by the Nyquist theorem. As a consequence, additional profiles have to be recorded in between, which requires a high positioning precision. As a completely identical response for the different antennas in an array is difficult to achieve, stripes can occur in the horizontal slices, especially when ringing occurs. This complicates the interpretation of features in the direction of the survey lines. In this paper, a three dimensional frequency-wavenumber filter is proposed, consisting in a combination of a circular filter and a fan filter. The application of this filter to GPR data collected at the Roman town Mariana (Corsica, France) showed a reduction of the stripe patterns, allowing a more reliable characterization of subtle archaeological structures.
The processing of aerial imagery acquired over Montarice hill (central Adriatic Italy) during the... more The processing of aerial imagery acquired over Montarice hill (central Adriatic Italy) during the Potenza Valley Survey will form the key focus of this paper. Since this site has repeatedly revealed itself in terms of interesting vegetation and soil marks, the most interesting footage, acquired during two observer-directed sorties more than a decade ago, will be examined. First, the potential of state-of-the-art image-based modelling (IBM) techniques is explored to create high-resolution orthophotographs from these analogue frame images. Since dense image matching-as a part of IBM-allows to model the vegetation surface at the moment of the photographic survey, a geometrical three-dimensional representation of the plant canopy is possible. This contribution shows how the latter can be the focus of its own information extraction process, using techniques mainly developed in the field of airborne laser scanning. However, the true interpretative power lies in the combination of the co-registered spectral and geometrical dimensions of the vegetation. Using Montarice as a case study, it will become clear that crop height data allows for powerful visualisations that can aid and even alter interpretative mapping that is solely based on colour differences in orthophotographs.
Uploads
Papers by Lieven Verdonck