Aerial photographs contain distortion because they do not maintain a constant scale across the image. Orthophotographs are more readily used for measurement and spatial analyses because they do maintain a constant scale across the image.

Orthophotos are digital images that are produced by making geometric corrections to scanned aerial photographs. The distortion in aerial photographs is removed by unwarping the effects of terrain, removing the perspective projection of the camera, and by fitting the image to a particular map projection to create an "image map" that has a uniform scale and a known accuracy. Hence, orthophotos can be used as a map whereas aerial photographs cannot. In computer systems, they can be integrated with other geographic information providing a rich visual context.

Find more information about orthophotos in our orthophotos section. The SCO also has a digital orthophoto demonstration and instructional toolkit available for download.