Resafa and Its Surroundings – Resafa-Sergiupolis / Rusafat Hisham the Employment and Evaluation of Diverse Methods
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Recording and Analysis of Field Data 1 Martin Gussone – Manfred Stephani – Dorothée Sack Resafa and its Surroundings – Resafa-Sergiupolis / Rusafat Hisham The Employment and Evaluation of Diverse Methods Abstract: The subject of the current investigation is the remains of the residence of the Caliph Hisham b. Abd al-Malik (724–742 AD) in the environs of the now ruined but still impressive city Resafa, situated between the Palmyrene desert and the river Euphrates in Northern Syria. The project “Resafa and its Sur- roundings” is notable for the wide range of techniques used. Over the course of several campaigns, geodetic measurements of large buildings have been taken, archaeological surveys and geophysical prospections have been carried out, the data for Digital Terrain Models has been recorded and aerial photographs have been rectified. In addition, archaeological excavations at selected sites were begun in autumn 2006. The current paper presents the application, interaction and results of the aforementioned methods, followed by an evaluation of the possibilities and limits of the techniques employed, illustrated by examples from the investigation of the residence. Resafa, City of Pilgrimage and Caliph Residence under the direction of J. Kollwitz. J. Kollwitz car- ried out a survey of the great Byzantine monuments Resafa, situated between the Palmyrene desert and inside the city walls and W. Karnapp investigated the river Euphrates in Northern Syria, served as a the city wall itself (Karnapp 1976). An Islamic pal- Limes Castrum in the Roman Empire, defending the ace outside the city walls was excavated by K. Otto- border with Persia. After the Martyrdom of Saint Dorn (Otto-Dorn 1957). The German Archaeologi- Sergios around 300 AD, Resafa flourished for cen- cal Institute (DAI) has funded the investigation of turies as a significant pilgrimage destination. The Resafa since 1976. T. Ulbert directed various inves- importance of the early city is documented by the tigations within the city until spring 2006. These ac- monumental churches as well as by large water cis- tivities comprised not only the excavation, record- terns, and an impressive city wall built up during ing and publication of investigations of Basilica A the 6th century. The worship of St. Sergios continued (Ulbert 1986), but also a topographical record of through the Islamic period into the Middle Ages the whole archaeological zone in 1976 by H. Tremel when the city was finally abandoned following the and, most importantly for our investigations, an invasion of the Mongols around 1250 AD. extended archaeological survey by M. Mackensen The subject of the current investigations is the (Mackensen 1984). This detailed survey located and remains of the residence of Caliph Hisham b. Abd mapped several objects of archaeological signifi- al-Malik (724–742 AD) in the southern environs of cance around and especially to the south of the city, Resafa. After his appointment as Caliph, Hisham and assigned to them short labels, for example PK built a large mosque adjacent to the main Christian for a palace complex (Palast-Komplex) or FP for a church, today known as Basilica A. Hisham, being a findspot (Fundplatz). D. Sack studied, recorded and man of the desert, erected his private residence out- published the investigation of Hisham’s mosque side the city of Resafa (Fig. 1). (Sack 1996) near Basilica A, and began as early as 1983 with a more detailed descriptive record of ar- eas of most probably Islamic settlements based on Early Archaeological Investigations the archaeological findings of M. Mackensen. In 1907 F. Sarre and E. Herzfeld rediscovered Resafa and published the first descriptions of the architec- Recent Activities in Resafa tural remains (Sarre / Herzfeld 1909). More exten- sive archaeological investigations, supported by the A more intensive study of the Islamic architecture German Research Foundation (DFG), began in 1952 and the remains to the south of the city was carried 2 Layers of Perception – CAA 2007 b. Abd al-Malik in the environs of Resafa are funded by the Fritz Thyssen Foundation. In the remainder of this paper, the methods and results of the sub- project “Rusafat Hisham – The residence of the Caliph Hisham b. Abd al-Malik” are presented in more detail. Archaeological Survey of the Islamic Remains Fig. 1. Aerial view from the south (M. Stephani, 1999). The Early Islamic buildings, situated mainly to the south of the city of Resafa, date back to the time of Hisham and were built mostly using mud brick. For out by D. Sack (Sack / Becker 1999), who suggested this reason these settlements are only noticeable as the probable uses of various places of interest, pro- small undulations on the desert surface. The outline viding insights into the location of buildings and of the walls are best seen when the sun is low, ei- their possible functions. Since 1997, a step-by-step ther in the morning or the afternoon. Digital Terrain documentation of the Islamic remains has been car- Models (DTMs) are best suited to model such small ried out, beginning with geophysical recordings undulations. Input data for the DTMs was the 3D (Becker et al. 2001). Two main geophysical record- coordinates of arbitrarily distributed points and so- ing methods have been applied so far. The magnetic called break lines, with which discontinuities of the anomalies of selected areas have been recorded and surface curvature could be described. In the case of chronicled by H. Becker, whilst F. Shouker has sup- small undulations, a dense set of precise points was plied electrical resistivity data for selected areas. required to obtain suitable results. Using the data Digital Terrain Models of local areas of interest have from the site, 3D points and break lines, a triangle been constructed by M. Stephani, and aerial photo- or “raster” based DTM was calculated and stored graphs were taken with a professional Rollei SLX by suitable software. The DTM data was then used 6 cm × 6 cm camera system in a helicopter flight to derive contour lines, cross sections, volumes, over Resafa and its surroundings in 1999. shaded reliefs, perspective views and other visual In order to undertake a deformation study of data. Basilica A and to determine any necessary restora- tion work, a larger GPS-based geodetic high preci- Archaeological Surveys: sion network was established by H. Heister in 2002 Levelling and Hand Measurements (Kowoll / Sternberg / Heister 2007). High preci- sion digital levelling was applied to determine the During the short spring period, humidity traces height of some seventy points inside and outside the of the walls can sometimes be observed directly Basilica A structures. The amount of deformation with the naked eye. By observing and interpreting was ascertained by repeating the measurements in the on-site undulations, it was possible to sketch a 2006, in conjunction with a terrestrial laser record- plan based on the archaeological survey with non- ing of the structures of Basilica A. Since 2006, the equidistant contour intervals, showing the outlines investigations in and around Resafa have been car- of buildings and even settlements. This preliminary ried out under the direction of D. Sack and a further method of direct observation, here called “archaeo- project phase with five subprojects has begun. logical levelling,” was used in combination with a There are still plans for an archaeological map DTM to interpret building structures. with chronological layers for the whole site, a more The archaeological levelling sketches were en- detailed survey of the city walls, strategies to devel- hanced by precise hand measurements. Outlines op preparations for restoration schemes, concepts of buildings, visible due to humidity traces and for site management, and last but not least, the ar- remains of plaster from the mud brick walls, were chaeological excavation of selected areas of the Is- marked out with pegs and cords. These “floor plans” lamic remains (Fig. 2). The investigations within were then measured with geodetic support (a total the city, including the city walls, are supported by station and a GPS). The reconstruction of the floor the German Archaeological Institute (DAI). The in- plans on-site by marking out the remains at the sur- vestigations of the residence of the Caliph Hisham face was essential to this process. The mere geodetic Recording and Analysis of Field Data 3 Fig. 2. Site map with palace complexes (PK), findspots (FP) and designation of areas of current investigations, 2001/ 2006 (D. Sack, M. Gussone, 2001). 4 Layers of Perception – CAA 2007 a. b. c. d. e. Fig. 3. PK V, combination of methods. 3a. Topographical survey, 1977: Outline of structures (Tremel, 1977). 3b. Archaeo- logical survey, 1983: interpreted sketch (D. Sack, 1983, CAD M. Gussone, 2001). 3c. Digital Terrain Model, 2001: Objec- tive contour lines (M. Stephani, 2001). 3d. Magnetogram, 1999: Subterranean condition (H. Becker, 1999). 3e. Combined interpretation, 2004: Interaction of methods (M. Gussone, 2004). measurement of the traces was not sufficient for a gorithms were applied. Geomagnetic recording later off-site reconstruction due to a lack of traces gave a less detailed representation of the archaeo- or poor visibility in some areas; a precise interpreta- logical structures than resistivity measurements, tion of the remaining traces and their relation was but required far less time. Ground penetrating radar enabled by reconstruction on-site. has not been used at this stage (Sack et al. 2004). Geophysical Prospections Photogrammetric Recording In 1997 a first geophysical prospection was conduct- The Islamic remains are spread out over a large ed in order to verify whether these methods would area, mainly to the south and southeast of the city be suitable for the non-destructive recording of mud of Resafa. As larger building structures and dis- brick remains in Resafa. Both the geophysical meth- tinct single settlements are distinguished, their ods applied produced unexpected and remarkable previous functions can, to some extent, be inferred results.