Evaluation of Corona and Ikonos High Resolution Satellite Imagery for Archaeological Prospection in Western Syria
Beck, Anthony, Philip, Graham, Abdulkarim, Maamoun, Donoghue, Daniel, Antiquity
An increasing number of archaeological researchers are routinely employing satellite imagery, particularly those working in western Asia (Ur 2003; Philip et al. 2002a; Kouchoukos 2001). The spatial, spectral, radiometric and even temporal resolutions of satellite imagery have developed to such an extent that they now share several of the physical characteristics of aerial imagery (see Tables 1 and 2). The value of satellite imagery is most obvious in those parts of the world, developing countries in particular, for which cartographic data is limited, aerial photography difficult to access, and archaeological inventories underdeveloped. The cost of satellite imagery can be low in comparison to that of a programme of dedicated aerial reconnaissance (contra Schmidt 2004). Competition between the main commercial vendors of fine resolution satellite data has prompted a marked reduction in cost, while the growing range of archive datasets should offer archaeologists access to a range of affordable digital data resources. In our view, satellite imagery will become ever more important for both research and heritage management particularly with the emergence of Google Earth and World Wind portals (Beck 2006). With this in mind, it seems appropriate to ask how effectively the capabilities of current datasets are being exploited and if synergies can be gained by employing data with different spatial, spectral, radiometric and temporal characteristics. It is important that archaeologists are fully aware of the benefits, limitations and methodological implications of using satellite imagery, as its misapplication may prove costly.
The research context
The archaeology of western Syria is particularly under-researched, with many areas providing minimal information on the nature, distribution and structure of settlement evidence in even the broadest sense. The project Settlement and Landscape Development in the Homs Region, Syria (SHR) was designed to address this problem by investigating long-term humanlandscape interaction in three adjacent but contrasting environmental zones, located in the upper Orontes Valley near the present-day city of Horns. Each zone is typical of a larger area, and initial study suggested that they differed substantially in both their settlement histories and in the nature of their archaeological records.
The project area consists of two study areas (Figure 1): the Northern Study Area (NSA) is located north-west of Horns and the Southern Study Area (SSA) to the south-west of Horns. The present discussion refers to the two most extensive landscape types, the marl landscape which constitutes by far the bulk of the 370[km.sup.2] SSA, and the 120 [km.sup.2] of basaltic terrain which characterises that part of the NSA located west of the Orontes River. For the wider aims of the project and detailed discussion of the study areas and current agricultural regimes the reader should refer to Philip et al. (2002b: 1-6) although a summary of the residue types in each zone is outlined here.
[FIGURE 1 OMITTED]
In the marl zone the majority of the archaeological residues takes the form of tells and low relief soil mark sites. We believe that these soil marks represent the decayed and thoroughly ploughed remains of abandoned settlements originally composed of mudbrick structures. In the basalt zone the archaeological residues take the form of cairns, field walls and concentrations of rubble which constitute the remains of abandoned structures (for an initial morphological classification of such structures see Philip et al. 2005: 36-8, Figure 6). The smallest of these features are stone alignments with a width of less than 1m, which in some cases, may project only a few tens of centimetres above the present ground surface.
Corona imagery and its limitations
It is important to summarise the use of Corona imagery so that the benefits of the more recent Ikonos imagery can be fully appreciated. …