4.3 Understanding the aerial and satellite images

4.3.1 What are we seeing in the aerial pictures?

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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Last updated: Mon Sept 29 2008