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Proceedings Paper

Motion-Error Immunity In Photo Coordinate Determination-A Novel Approach To The Absolute Comparator
Author(s): James R. Pekelsky
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Paper Abstract

The comparator is a device facilitating both the delineation of features of an object via some indicating means and determination of their relative spatial coordinates from a scale. The concept is fundamental to spatial measurement and is embodied in a broad spectrum of instruments ranging from the simple shop micrometer to the sophisticated photogrammetric plotters. All compare object to scale and can be discussed in terms of mapping scale space into object space. The absolute comparator is the ideal; the mapping is one-to-one, undistorted and uncorrupted, ie. the mapping is error-free. In the real-world, the mapping is physically embodied as the mechanical linkage between the viewing and measuring systems, so that residual bearing play and runout, plus the plastic flexibility of linkage elements result in motion-error which manifests as mapping errors. Motion-error is often the dominant error component in coordinate measurements and presents a major hurdle in state-of-the-art comparator technology. There are three approaches to the motion-error problem: reduction, compensation and immunization. The first is a matter of mechanical refinement and finesse, while the second relies upon brute-force calibration and/or measurement over-determination. The third approach involves a concept so simple it has been essentially overlooked despite its far-reaching implications. The theoretical considerations and evolution of an experimental prototype comparator enjoying motion-error immunity are presented.

Paper Details

Date Published: 12 December 1981
PDF: 19 pages
Proc. SPIE 0309, Airborne Reconnaissance V, (12 December 1981); doi: 10.1117/12.932780
Show Author Affiliations
James R. Pekelsky, National Research Council of Canada (Canada)

Published in SPIE Proceedings Vol. 0309:
Airborne Reconnaissance V
Robert J. Bannach, Editor(s)

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