Since the 1940s aerial imagery has been the primary source of detailed geospatial data for extensive study areas. Photogrammetry is the profession concerned with producing precise measurements from aerial imagery. Aerial imaging and photogrammetry comprise a major component of the geospatial industry. The topics included in this unit do not comprise an exhaustive treatment of photogrammetry, but they are aspects of the field about which all geospatial professionals should be knowledgeable.