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Proceedings Paper

Contour Generation Using Fourier Transform Filters
Author(s): John R. Benton
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Paper Abstract

The last decade has seen an increasing inter-est in developing alternatives to manual stereocompilation. These new methods have ranged from electronic cross-correlation to optical cross-correlation and match filtering (Ref. 1-3). This paper discusses a technique of generating a complete set of contours using a relatively simple optical apparatus. Over-lapping stereophotographs are coherently summed using a Mach-Zehnder Interferometer. For vertical photography the y-parallax can be removed by proper orientation of the film plates and the only remaining x-parallax is due to terrain elevation differences. This parallax will result in a grating-like structure that can be bandpass filtered in the Fourier Transform plane to pass some given grating spacing and the corresponding parallax. The filtered image will contain a constant parallax contour, which for vertical photography is a constant height contour. Since the grating-like structure is not sinudoidal, higher order frequencies will be present and harmonic frequencies corresponding to multiples of the parallax associated with the filter frequency will also be present and produce additional contour fringes at a reduced modulation in the image.

Paper Details

Date Published: 1 October 1974
PDF: 6 pages
Proc. SPIE 0045, Coherent Optics in Mapping, (1 October 1974); doi: 10.1117/12.953974
Show Author Affiliations
John R. Benton, U.S. Army Engineer Topographic Laboratories (United States)

Published in SPIE Proceedings Vol. 0045:
Coherent Optics in Mapping
N. Balasubramanian; Robert D. Leighty, Editor(s)

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