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Combining data of different GPR systems of surveys of the roman fort Qreiye-cAyyash, Syria

S. Seren, Alois Hinterleitner, M. Gschwind, Wolfgang Neubauer et Klaus Löcker
p. 353-355

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Introduction

1The Roman fort of Qreiye-cAyyash was founded in the late 2nd or early 3rd century AD and was abandoned in the mid-third of the 3rd century AD. It is situated immediately north of the modern village of cAyyash, 12 km upstream from Deir ez-Zor in Syria, on the edge of a plateau overlooking the valley of the river Euphrates. The Roman fort comprises 220 x 220 m and was discovered in 1929 by A. Poidebard in the course of an aerial photographic reconnaissance (Poidebard, 1934, 87-88, pls 86-87).

2In spring 2002, the German Archaeological Institute Damascus and the Direction General of Antiquities and Museums of Syria established a joint project to investigate the site by carrying out systematic topographical and archaeological surveys, magnetic and geoelectric prospection and archaeological excavations (Gschwind-Hassan, 2008; Gschwind, 2003-2007).

GPR prospection

3In November 2002, a GPR test survey of 9 700 m2 was carried out successfully by Archeo Prospections® in the central area of the fort (Seren et al., 2007), using a PulseEKKO 1000 with 900 and 450 MHz antennas. The GPR prospection of the entire area of the fort was possible thanks to generous support from the Gerda Henkel Foundation. It was completed in September 2004, using a PulseEKKO 1000 system with 900 MHz antennas and a GSSI SIR-3000 system with 400 MHz antennas. Further GPR prospection inside and outside the Roman fort was carried out in October 2005 using a Noggin system with 500 MHz antennas (Fig. 1). In total, an area of more than 75 000 m² was prospected using GPR.

Figure 1: GPR prospection at the edge of the plateau immediately north of the Roman fort of Qreiye using a Sensor&Software Noggin System with 500 MHz antennas.

Figure 1: GPR prospection at the edge of the plateau immediately north of the Roman fort of Qreiye using a Sensor&Software Noggin System with 500 MHz antennas.

Data Processing

4For computing depth slices, a mean velocity of 12.5 cm/ns is used, the GPR traces are suitably band-pass filtered and a background removal filter is applied (Fig 2). The partly overlapping single GPR grids are put together in one 3D data block with 10 cm depth slices by averaging overlapping areas.

Figure 2: GPR depth slice 0.20-0.40 m. Archaeological structures show partly very good and partly very small contrast and are overlaid by striping patterns in the measuring direction.

Figure 2: GPR depth slice 0.20-0.40 m. Archaeological structures show partly very good and partly very small contrast and are overlaid by striping patterns in the measuring direction.

5The prospection results are very different depending on the location and the GPR-System (Fig. 2). Due to the rough surface the PulseEKKO 1000 system produces a very distracting striping pattern in the measuring direction on visualisations of depth slices. The geophysical contrast of archaeological structures seems to be insignificant in some areas and substantial in others. Therefore, certain archaeological structures are visible very clearly, while others are hardly recognisable and some areas are entirely devoid of visible archaeological features. The expected archaeological structures (walls) are generally composed of mud-brick resting on foundations of magnetic quarrystone. The fort of Qreiye is situated on a plateau formed of a basalt layer 2-3 m thick and overlaid by natural clay and debris from collapsed mud-brick (Kiss 2006). The basalt is strongly and variably magnetic. Therefore, only the most solid archaeological structures could be detected by magnetic prospection.

6The GPR profiles were carried out at an angle of 45 degrees to the expected rectangular archaeological structures to get equally good response for all directions of the structures, although this leads to a much higher effort in the field. Since it is necessary to apply an average trace removal filter with a filter-length of only 1 m, the linear archaeological structures would also be removed, if they were oriented in the direction of GPR profiles. The 1 m average trace removal filter leads to depth slices with significantly less noise and nearly no disturbing linear patterns in the GPR profile direction (Fig. 3).

Figure 3: GPR depth slice 0.20-0.40 m. The striping patterns disappear with the use of an average trace removal filter with only 1 m length.

Figure 3: GPR depth slice 0.20-0.40 m. The striping patterns disappear with the use of an average trace removal filter with only 1 m length.

7To enhance archaeological structures with very small geophysical contrast a Wallis-filter (Wallis, 1977) with 12 x 12 m window size has been applied (Fig. 4). The Wallis-filter changes the statistical parameters mean and standard deviation so that they are the same for the applied window size at any location in the image. Therefore, archaeological structures with small geophysical contrast are statistically enhanced. Because a very dense cover of buildings can be anticipated inside a Roman fort, a 12 x 12 m window is used. The Wallis–filtered visualization is helpful as an additional source for archaeological interpretation.

Figure 4: GPR depth slice 0.20-0.40 m. A Wallis-Filter with a 12 x 12 m window enhances archaeological structures with very small geophysical contrast.

Figure 4: GPR depth slice 0.20-0.40 m. A Wallis-Filter with a 12 x 12 m window enhances archaeological structures with very small geophysical contrast.
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Bibliographie

Gschwind, M. and Hasan, H., 2008. Das römische Kastell Qreiye-cAyyāš, Provinz Deir ez-Zor, Syrien. Ergebnisse des syrisch-deutschen Kooperationsprojektes. Zeitschrift für Orient-Archäologie 1: 316-334.

Gschwind, M., 2005. The Roman Fort Qreiye/cAyyash on the middle Euphrates River. InPlaces in Time. 25 Years of Archaeological Research in Syria, 1980–2005, Damascus 2005, 122-127.

Kiss, T., 2006. Geomorphological Description of the Neighbourhood of Tall ar-Rum and Qreiye-cAyyash, Damaszener Mitteilungen, 15: 383-387.

Poidebard, A., 1934.La trace de Rome dans le désert de Syrie. Le limes de Trajan a la conquête arabe, Bibliothèque Archéologique et Historique 18, Paris.

Seren, S., Eder-Hinterleitner, A., Neubauer, W., Löcker, K. and Melichar, P., 2007.Extended Comparison of Different GPR Systems and Antenna Configurations at the Roman Site Carnuntum, Near Surface Geophysics, 5 (6): 389-394.

Wallis, R., 1976. An approach to the space variant restoration and enhancement of images. In C. O., Wilde, E., Barett (dir.). Proceedings, Symposium on Current Mathematical Problems in Image Science, Montery, CA, Nov. 1976, reprint, Image Science Mathematics, Western Periodicals, North Hollywood, Ca.

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Table des illustrations

Titre Figure 1: GPR prospection at the edge of the plateau immediately north of the Roman fort of Qreiye using a Sensor&Software Noggin System with 500 MHz antennas.
URL http://archeosciences.revues.org/docannexe/image/1829/img-1.jpg
Fichier image/jpeg, 208k
Titre Figure 2: GPR depth slice 0.20-0.40 m. Archaeological structures show partly very good and partly very small contrast and are overlaid by striping patterns in the measuring direction.
URL http://archeosciences.revues.org/docannexe/image/1829/img-2.jpg
Fichier image/jpeg, 548k
Titre Figure 3: GPR depth slice 0.20-0.40 m. The striping patterns disappear with the use of an average trace removal filter with only 1 m length.
URL http://archeosciences.revues.org/docannexe/image/1829/img-3.jpg
Fichier image/jpeg, 524k
Titre Figure 4: GPR depth slice 0.20-0.40 m. A Wallis-Filter with a 12 x 12 m window enhances archaeological structures with very small geophysical contrast.
URL http://archeosciences.revues.org/docannexe/image/1829/img-4.jpg
Fichier image/jpeg, 548k
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S. Seren, Alois Hinterleitner, M. Gschwind, Wolfgang Neubauer et Klaus Löcker, « Combining data of different GPR systems of surveys of the roman fort Qreiye-cAyyash, Syria », ArcheoSciences, 33 (suppl.) | 2009, 353-355.

Référence électronique

S. Seren, Alois Hinterleitner, M. Gschwind, Wolfgang Neubauer et Klaus Löcker, « Combining data of different GPR systems of surveys of the roman fort Qreiye-cAyyash, Syria », ArcheoSciences [En ligne], 33 (suppl.) | 2009, mis en ligne le 30 octobre 2011, consulté le 16 août 2017. URL : http://archeosciences.revues.org/1829 ; DOI : 10.4000/archeosciences.1829

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Auteurs

S. Seren

Central Institute for Meteorology and Geodynamics, Hohe Warte 38, A-1190 Vienna, Austria (Sirri.Seren@zamg.ac.at)

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Alois Hinterleitner

Central Institute for Meteorology and Geodynamics, Hohe Warte 38, A-1190 Vienna, Austria

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M. Gschwind

c/o Institute of Prehistory and Archaeology of the Roman Provinces, University of Munich, Geschwister-Scholl-Platz 1, D-80539 München, Germany

Wolfgang Neubauer

Vienna Institute for Archaeological Science, University of Vienna, Franz Klein-Gasse 1/V, A-1190 Vienna, Austria

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Klaus Löcker

Central Institute for Meteorology and Geodynamics, Hohe Warte 38, A-1190 Vienna, Austria

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