Geographic Information Systems (GIS)
CLAS uses a range of state-of-the-art technology to access and manage the remote human past, including satellite imagery, aerial photography, ground-based GPS, and Geographic Information Systems (GIS) software. GIS was used to create a predictive model for site location based on known sites and their relationships with each other. This will guide future survey, especially during the CLAS 2009 field season.
Also central to the project is the recent history of the landscape, including threats to the burial mounds, or tumuli, of Bin Tepe due to illicit looting as well as urban and agricultural expansion. Focus has been on examining recent satellite imagery and past aerial photos of the landscape to monitor its changes over time. GIS software is used to assist in the development of a sustainable heritage management plan for the protection of archaeological and ecological zones.
Creating an Extensive Digital Database
By digitizing various features of a topographic map of the area, we have created a wide range of data that can be manipulated and analyzed. This includes canals, roads, villages, tumuli, the Gediz River and the Gygaean Lake, as well as contour lines that are used to create the DEM. Using ArcGIS and ENVI, the aerial photography, satellite imagery, and vectorized maps were given accurate geographic locations that coordinate with the precise GPS data collected in the field. This database provides the foundation for all future archaeological survey and work on heritage management and sustainable development in the survey area.
GPS field data come from a Topcon Real-Time Kinematic HiperLite+ GPS+ system. “Real-Time Kinematic” means that the spatial data is collected while the rover units are in motion and is immediately displayable and editable in the field. The system relies on a base unit which automatically locates itself relative to as many satellites as possible, and communicates with “rover” units which collect spatial data with accuracy of 1 centimeter horizontally and 3 centimeters vertically.
Site Location Profile
The network of 2nd Millennium BCE fortified sites is one of the most noteworthy archaeological features in the survey area. The site location profile identifies survey targets based on:
- topographic location on a hilltop or ridge relatively low in the foothills.
- a peak in slope values at approximately 15 degrees.
- visibility between the sites and of the agricultural plain.
- about 5 km walking distance between neighboring sites.
Predictive modeling such as this site location profile guides field survey and aids in our understanding of inter-site relationships during the Middle to Late Bronze Age in Western Turkey.
Computer-based Analyses: Visibility and Distance
There are at least five contemporary fortified Middle to Late Bronze Age sites surrounding the modern lake. In this network, the topography of the sites is an artifact of the human settlement which once existed there. Surface-based analysis is one focus of the tools available to an archaeologist once a digital elevation model (DEM) has been created. These tools allow archaeologists to delve into the reasons for settlement at a certain place. The position of the fortified sites in the foothills around the plain suggests that visibility was a key consideration for inter-site communication. The “viewshed” tool in ArcGIS creates a raster with areas that are visible and not visible from user-chosen observer point. While straight-line distance on a map is sometimes useful, in archaeology the walking distance between two sites is often a more practical piece of information. The “least-cost path” tool in ArcGIS finds the easiest way to travel between two points on a surface based on user-defined limiting factors; in this case, slope angle. By finding common elements in the placement of sites and their topography, the CLAS team will focus future survey seasons to try to discover if any more fortified sites exist.