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July 2003-July 2010InteractiveDig Sagalassos
Coring with the Ramguts drill inside the west portico of the Colonnaded N-S Street, where a fill of more than 3 m thickness had been spread out to level the area.
Panoramic picture of a part of the Çanakli Ovasi
ASTER satellite image of the same zone (indicated by the red rectangle)

Photos courtesy Sagalassos Archaeological Research Project. Click on images to enlarge.
by Marc Waelkens

Geomorphological Survey: August 21-25, 2005

At the beginning of the week, the geomorphological team composed of Etienne Paulissen, David Kaniewski and Véronique De Laet (all KULeuven) used the Ramguts drill for coring inside the test sounding trench below the pavement of the North-South Colonnaded Street and below the exposed portico section along the west side of it (see Colonnaded Street, July 31-August 4). These corings confirmed the enormous leveling activities carried out in early Imperial times to build this street: whereas the 1.75 m deep trench in the middle of the street was sitting almost directly above the ophiolithic bedrock, meaning that a 1.80 m thick fill had been spread out here to level the area, this proved to have been ca 3.20 m below the portico!

During the rest of the week the geomorphological team has surveyed in the Aglasun-Çanakli valley, to the south of Sagalassos, to verify the spectral information contained in the ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) satellite images. ASTER, an imaging instrument flying on board of the TERRA satellite has a spatial resolution of 15 m in the VNIR (Visual near Infrared: 3 spectral bands and 1 stereoscopic band), of 30 m in the SWIR (Short Wave Infrared: 6 bands) and of 90 m in the TIR (Thermal Infrared: 5 bands). A combination of different bands provides information on landscape parameters such as vegetation, soil composition, water content and geology.

Some information on the image seems to be straight forward, but has still to be checked in the field. As an illustration: the false color image of part of the Aglasun-Çanakli Ovasi (Aster Image, October 18, 2001: see red rectangle) is compared with a photograph taken this week. On both images the arable land (sun-flowers on the photograph) on the alluvial fan deposits is clearly distinguished from the Poaceae (typical grasses) and the Cyperaceae (typical wetland herbs) in the seasonal inundated marshes.

The possibilities of such images are however much greater. One of us (Véronique De Laet) has worked out different band combinations. Within the VNIR bands, a differentiation between irrigated and non-irrigated agricultural fields was feasible, as well as the identification of main vegetation zones (evergreen and deciduous trees), arable fields, grasslands, bare soils and rock outcrops.

When VNIR and SWIR bands are combined (for specialists:) not directly visible information can be extracted, such as the water content, the sedimentological and mineralogical characteristics of recent deposits. During this week, we have studied the vegetation characteristics and sampled transects crossing zones with different characteristics. The aim is to examine whether or not soil parameters as defined in the lab will correlate with the reflectance information contained in the combined bands. The first results are very promising. It is however already clear that the interpretation of the sedimentological band combination is not identical (vegetation, water content and soil characteristics interfere with each other) for all areas in the vicinity of Sagalassos and that every area should be interpreted separately. Yet, it offers tremendous possibilities to study present and past types of land use.

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