Stereo-Topographic Mapping

This paper begins with a general introductory statement of the relative advantages of aerial and ground-survey methods in topographic mapping. A discussion of the fundamental principles of stereoscopic measurements is given to prepare the reader for a better understanding of the mechanical features involved in the construction of measuring stereoscopes. A description is given of some of the instruments in use at present for making topographic maps from photographs taken in the air. The theory of the aerocartograph is described in detail because that is the instrument with which the writer is most familiar. However, it is intended that this description be considered merely the “ground work” for a general theory and that discuss ion will produce comments on similar instruments in so far as they vary from the aerocartograph, on the advantages and disadvantages of the various types, and on general suggestions for improvement based on experience.