Decoding Aerial Photographs

Centuries of cultivation have levelled most of the archaeological sites in Strathearn. It is only through aerial reconnaissance that the richness of archaeological remains can be recognised. In dry conditions differential ripening of crops can reveal the presence of buried features such as ditches and pits which are revealed as cropmarks. In the 1970s whilst searching for cropmarks of Roman military camps, Professor J.K. St. Joseph discovered the great Forteviot prehistoric ritual complex. Since then this area has been flown on numerous occasions, in different conditions and under different crops allowing archaeologists to build up a comprehensive view of the buried archaeological landscape.

Translating the patterns seen in the vegetation into meaningful archaeological information requires special expertise. The cropmarks can be faint and in the Strathearn region they are often obscured by geological features within the soil – as can be seen in the darker blank areas on the photographs in the monitor. It is only after a consideration of photographs from many seasons that the complete site can be mapped with confidence and, as we have discovered, excavation always reveals more features than can be seen from the aerial photographs.


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