We have used several types of air photographs to study Greek and Roman city planning and land organization in the Corinthia. There exist both low altitude as well as high altitude photographs of the area as well as some very low level balloon photographs. Low altitude air photographs, at an approximate scale of 1:6000, taken in 1963 by the Hellenic Air Force, correspond very well with the 1:2000 topographical maps, which were made in the same year using the air survey. The air photographs have been useful for a number of reasons. Shadows and vegetation or soil markings highlighting unexcavated underground features in the landscape, such as roads, ditches or structures are visible. These features can be helpful when put together with other forms of information, such as the surveyed and excavated roadways.
Before performing any analysis of any of the photographs it is necessary to first rectify its geometry in calibration with the existing maps and surveyed data. Therefore, each photograph is scanned at the resolution of 400 dpi (dots per inch) using a desktop flatbed scanner (UMAX PowerLook 2100XL) and rectified using the resampling program included in CAD Overlay, (discussed below under GIS applications). The control points needed for this operation are taken from the topographical maps. The corners of buildings or the intersection of field boundaries have proven to be most precise. Once the photograph has been successfully rectified, it is possible to display it as a backdrop to the AutoCAD drawings using CAD Overlay. In this way one is able to trace over the crop and soil marks and study them in conjunction with other surveyed or map data.
High altitude air photographs at a scale of approximately 1:37,500, taken in 1987 by the Greek Army Mapping Service, have helped us to understand the overall pattern of the roads and field boundaries in the larger terrain surrounding Ancient Corinth. Control points necessary to rectify these photographs are taken from the topographical maps or satellite images, where we do not have a detailed map of the entire area covered by the photograph.
A series of low level balloon photographs at an approximate scale of 1:1750 taken by Dr. and Mrs. J. Wilson Myers in 1986 have greatly assisted in the identification of details in the landscape at the Roman harbor of Lechaeum. These balloon photographs have been successfully rectified to both the low level air photographs as well as the 1:2000 scale topographical maps.