Results and Discussion
Image composites for morning and evening data obtained at New Philadelphia are shown Figure 2, below. There is a considerable amount of variation between the two data sets. The morning image is dominated by surface features and, as a result, it is difficult to identify anomalies that might be archaeologically significant. There is extensive shadowing visible to the west of the trees and this is probably highlighting the surface features.
Unfortunately, it was not possible to avoid shadowing in the morning data. Flying earlier, before the sun is high enough to cause shadowing, would decrease the amount of heat that penetrates into the ground. The chances that buried archaeology would be visible are very small. Flying late enough in the day to eliminate shadowing would not be safe.
The surface features were deemphasized in the evening data since flights were just before or just after sunset. There are more features of potential archaeological significance in this data than the morning data.
Anomalies were identified as hot or cold and coded on vector layers (Figure 3) for both data sets. Only anomalies that were not related to obvious surface features were included. Features such as stone foundations, characterized by low conductivity and low thermal inertia, should be visible as positive or hot targets in the morning and negative or cold targets in the evening. A pit is a type of anomaly that might show the converse thermal behavior (negative in the morning and positive in the evening).
Bryan Haley also created a database display, using Geographic Information System (GIS) software programs, of these data sets for the resulting analysis. The GIS database consists of two raster (the thermal infrared composites in Erdas Imagine format) and two vector (the interpretation polygons in ESRI shapefile format) files. In addition, an ArcMap document was created that contains all four of the data sets.
A series of oblique images were also collected, covering areas away from the site core. These areas were not included in the composite image since these down-slope areas are heavily disturbed and the extreme oblique angle of these images.