an opticomechanical device for making various measurements of object images in terrestrial, aerial, and space photographs in the process of stereoscopic examination. Stereometers have parallactic devices and a measuring mark that is displaced over a three-dimensional model of the terrain (or of a separate object) re-created on the instrument. Depending on the purpose, various types of stereometers are distinguished. Topographic stereometers are used for sketching topography and for aerial photo interpretation in map-making. (The most effective Soviet stereometer was designed by F. V. Drobyshev.) Precision stereometers are used for making exact photogrammetric determinations, and geological stereometers, for measuring from photographs the rock bed positions.