As most of the archaeologists do we also used within the Emptyscapes project two types of air photography: ‘oblique’ or perspective views and ‘vertical’ photography, pointing straight downward at the earth’s surface.
Vertical photography (originally analog but now more frequently digital) is taken with sophisticated cameras from specially equipped aircraft, mainly for survey and mapping purposes. It is relatively expensive and archaeologists can rarely afford to commission it for their own purposes. For most purposes they therefore draw on the vast collections of air photographs already available in existing archives. During the Second World War the fighting powers took between them approximately 50 million aerial photographs. In Europe public services collect perhaps millions more frames each year.
Oblique photographs are generally taken by archaeologists themselves, from the open window of a two-seater or four-seater light aircraft, hired from a local airfield (or occasionally owned by the archaeologists themselves or by their employers). The cameras and films are quite simple and inexpensive.
While vertical photography records the whole of the landscape, oblique photography covers only what the photographer sees and judges to be archaeologically significant.