Tri-Bar Reading Correction for Oblique Imagery
Final rept. Dec 1978-Jul 1979
AIR FORCE AVIONICS LAB WRIGHT-PATTERSONAFB OH
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Tri-Bar resolution targets are geometrically distorted when photographed at oblique angles. One of the effects of this distortion is the changing of the aspect length to width ratio of the bars. Targets parallel to the line of flight crossline at large oblique angles to nadir of the aircraft produce images with apparent increased aspect ratios due to the foreshortening of the barspace width. Perpendicular targets to the flight direction inline at an oblique angle have their lengths foreshortened, thus reducing the aspect ratios. At 70 deg, original 51 aspect ratio tri-bar targets have apparent ratios of 14.61 crossline and 1.711 inline. A laboratory experiment was set up to simulating oblique imagery to determine what effects the changing aspect ratio has on the accuracy of tri-bar readings, after the insertion of normal geometrical corrections. Different target contrast ratios, target orientations, and cameras were used. Analysis of variance showed that for crossline targets, resolution readings corrected by the normal cosine geometrical factor provide accurate results for any contrast ratio or target orientation.
- Cartography and Aerial Photography
- Human Factors Engineering and Man Machine Systems