Interactive precise measurement of relative orientation points using least squares correlation
Susumu Hattori, Akiyoshi Seki, Sugao Gyoji, Atsushi Okamoto · Systems and Computers in Japan · 1997
The authors are now developing the GOKU digital image-based plotter for producing topographic maps from aerial photographic images. The precision of relative orientation governs the precision of plotting. For keeping the intrinsic plotting precision, the coordinates of the relative orientation points must be measured to subpixel order, because the pixel size is limited in practice. In addition, automation of coordinate measurement is much needed in order to alleviate tedious work. This paper proposes a method of semiautomatic measurement of relative orientation points with high precision and stability. Conventional correlation and least squares correlation (LSC) have previously been employed for this purpose. But the latter is unstable if used arbitrarily, and the precision obtainable by the former has been little reported. This paper examines both methods experimentally and shows that LSC is superior. It also examines the precision and stability of LSC with reference to parameters (correlation window size and degree of freedom). Since the instability of LSC is due to excessively narrow convergence domains, they are widened procedurally by using two edge extraction filters. The expected precision of the measurements as a result of this improvement is 1/3 pixel. © 1997 Scripta Technica, Inc. Syst Comp Jpn, 28(3): 34–42, 1997