GIS orthographic digitizing of aerial photographs by terrain modeling

Spatial data digitized from individual raw aerial photographs are corrected analytically to update a geographic information system (GIS) database. The collinearity correction model is compiled by applying digital terrain data and a suitable base of horizontal control. This method, photo-digitizing, allows spatial databases to be updated from digitizer workstations without photogrammetric equipment and processing. Data entry staff do not require special photogrammetric training. From testing on surveyed ground targets, thee accuracy of photo-digitizing (5.5 ± 3 m) exceeds that achieved with current field data and procedures. Field staff retain ownership of data and control of the update process