Topographic Plotter

a stationary instrument for interpretation of aerial photographs. It makes possible the stereoscopic interpretation of black-and-white or color aerial photographs taken in one or more scales (up to 1:7.5) in transmitted or reflected light. The magnification may be 2 X for overall viewing or may be smoothly varied up to 15 X for the study of individual sections of an aerial photograph. Magnification, brightness, and optical rotation are adjustable either simultaneously for a stereoscopic pair of aerial photographs or separately for each of them.

The viewing system of the instrument includes reference points and a scale for measuring object images in the horizontal and vertical planes. The parallax difference may be read to an accuracy of 0.02 mm. A special carriage makes it possible to work with aerial photographs up to 30 X 30 cm in size without moving them on the instrument table. In addition to their main purpose, topographic plotters are also used for examination of terrestrial and laboratory stereo photographs and for optical transfer of identified contours and points from one photographic material to another. Some instruments are made with dual eyepieces (the “consultative version”) and with attachments for simple mapping work. The main manufacturer of topographic plotters is the state Carl Zeiss Optical Works in Jena (German Democratic Republic).