Traditionally, such photographs are obtained from a light, low-flying aircraft taking vertical or, more commonly, oblique photographs. With the advent of high-resolution satellite imagery, archaeologists have another imagery source at their disposal. Aerial Archaeology Roman Colosseum. To the left of the amphitheater, the remains of the Temple of Venus and Rome and The Forum can be seen. Features apparent on aerial photographs are often described according to how they're revealed and can range in size from earthworks several kilometers long to soil marks and crop marks less than a meter wide.
Earthworks are features that can be seen in relief.
They are usually apparent on aerial photographs as highlights and shadows but also may be seen as differences in vegetation cover, as well as differential melting or drifting of snow. Their appearance is highly dependent on weather and lighting conditions and tends to be seen best when the sun is low in the sky. Soil marks reveal the presence of buried ditch banks or foundations through changes in soil color revealed when parts of the buried feature are brought to the surface by plowing. Such features, gradually being destroyed by modern cultivation, are most apparent in aerial photographs taken during the winter when fields are free of crops. Buried walls and ditches also can be detected as crop marks where the presence of the buried feature decreases or enhances crop growth as a result of differences in moisture and nutrient availability.