Photogrammetry with surface-based images

Stereoscopic pictures returned by surface-based imaging systems can be used to reconstruct the topography of landing sites on Mars and other planets. Large surface relief with respect to distance and the large scale variation inherent in surface-based pictures produce problems in stereoscopic measurement very different from those presented by high altitude photography. Optical-mechanical scanning systems, or facsimile cameras, facilitate accurate reconstruction of landing site topography because of the linearity of system photometric response and the accuracy with which image geometry can be measured.