C-Factor for softcopy photogrammetry

The C-factor is an empirical value based on the precision of the photogrammetric instrumentation. The conventional C-factor has been used successfully over the years to determine the flying height required to produce a specified contour interval. C-factors for conventional instruments range from 900 to 2200 with 2200 being typical of state-of-the-art analytical plotters. Today's trend away from analog and computer-assisted plotters to digital photogrammetric workstations calls for a C-factor to use when the photogrammetry is to be accomplished using softcopy photogrammetric workstations. The soft C-factor will be based on conventional mathematics developed for analog instruments and related to today's cameras, scanners and soft copy workstations. Typical soft C-factors for digital photogrammetric workstations, assuming standard aerial photography and different scan spot sizes, are in a range from 800 to 2200.