Tri-Bar Reading Correction for Oblique Imagery
Abstract
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 bar/space 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 5:1 aspect ratio tri-bar targets have apparent ratios of 14.6:1 crossline and 1.71:1 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1979
- Accession Number
- ADA076340
Entities
People
- Edward L. Gliatti
- Thomas Stanzione
Organizations
- Air Force Research Laboratory