Photogrammetry is the art and science of obtaining reliable measurements by photography (metric photogrammetry) and qualitative evaluation of image data (photo interpretation). It includes use of terrestrial, close-range, aerial, vertical, oblique, strip, and space photographs along with their interpretation.

Scale formulas are as follows:

Photo scale=ab/AB=f/(H-h₁)

where f =focal length of lens, in (m)

H =flying height of airplane above datum (usually mean sea level), ft (m)

h1 =elevation of point, line, or area with respect to datum, ft (m)