The contrasting areas of light and dark on the aerial photographs and satellite images are a product of four factors, each of which may be indicative of the buried archaeology:
| Factor | Cause |
|---|---|
| Lighting | Sunlight striking the uneven ground surface: highlighting higher ridges and casting shadows according to the angle of the sun. |
| Vegetation | Differential areas of plant growth, reflecting both ground moisture/drainage and soil compaction. |
| Soil colour | Reflecting differing soil composition (e.g. amounts of charcoal, building material, organic materials), or moisture levels (reflecting drainage and differential drying). |
| Soil texture | Reflecting compaction (e.g. hard smooth surfaces, areas of uneven surface/animal disturbance). |
All of these factors can change on a daily or seasonal basis, which highlights the advantages of using multiple images, taken at different times of the day and year.
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URL: http://intarch.ac.uk/journal/issue25/1/4_3_1.html
Last updated: Mon Sept 29 2008