Abstract: A photogrammetric plotting apparatus comprises means to move two stereographic plates in their plane with respect to two respective optical systems which are arranged to project onto a single screen images of reference marks indicating the trace of the line of sight of each optical system on the respective plate. Different polarizers are disposed on the lines of sight of the optical systems so that an operator looking at the said screen through two analyzers corresponding to the polarizers sees the images of the region of one plate and its respective reference mark with one eye and the image of the corresponding region of the other plate and its respective reference mark with the other eye.