Abstract
This paper describes an experimental system for generating contour lines automatically from stereopaired photographs. The system consists of a pair of projectors, a 32×32 integrated photodiode array mounted on an XY-recorder and a small computer PDP-12 with 8K-word core memory. Contour lines are generated directly from a pair of optically projected images, not by evaluating elevations over the entire field.
The XY-recorder is placed vertically on the floor and on its recording plane a pair of stereo images is projected alternatively from the left and right projectors. The image pair reconstructs a virtual relief, and contour lines associated with an elevation value are obtained by cutting the relief by recording plane. The photodiode array is mounted just on the pen position to detect a pair of image segments; one is a 3.2×3.2mm2 area of the left projector image and the other is that of the right projector image. The computer compares the segments and controls the movement of the detector. At each step of the generation process the detector is moved to such a position that the pair images become most alike. The trajectory of the detector movement is recorded by the pen; generating a contour line.
