INVESTIGATION OF FUSION AND FIXATION DISPARITY LIMITS FOR PHOTOGRAMMETRY.

Fixation disparity is a phenomenon associated with normal binocular vision which causes an observer to perceive a fixated point in space in front of or behind its actual location in physical space. Considering the floating mark settings which are fundamental to photogrammetric measurements, any such settings made by an observer when fixation disparity is present will contain errors of a constant nature which will vary with the viewing conditions and with time. Previous studies of the phenomenon have been of a basic nature and, in general, have not been directly related to the needs of photogrammetry. It is the purpose of this project, therefore, to investigate the effects of fixation disparity on floating mark measurements made under photogrammetric conditions using variable measuring marks, variable targets and variable backgrounds.