Use of weighted least squares for geo-positioning using dual-satellite image pairs

Abstract

This study investigates the use of weighted least squares (WLSs) estimation for geo-positioning using dual-satellite image pairs. Although many believe that the WLS method may be the optimal method for handling such pairs composed of different-resolution images, this study reveals that it has not been thoroughly validated using real satellite data and has obvious limitations for the space intersection of dual-satellite images, despite its potential. In addition, this article addresses the fact that the positioning accuracy may depend on the geometric conditions, as well as the resolution. This study visually and quantitatively checked the effect of the WLS method on the positioning accuracy using all the dual-satellite pairs available from two KOMPSAT-2, IKONOS, and QuickBird images. The results reveal that the WLS method is very effective for horizontal mapping. This observation was also valid in principle even for three rays, with a higher-resolution single image integrated into an existing stereo pair. In particular, it tends to cause a larger improvement when the pairs form a weaker geometry, which increases the spatial uncertainty near the intersection point. However, the WLS method did not improve the vertical mapping. It yielded a lower accuracy than the conventional approach, particularly in the case of three rays, owing to the weak convergence geometry created by integrating different-satellite images. This indicates that the WLS method must be conditionally accepted for mapping using dual-satellite images. This article demonstrates the potential and limitations of WLS estimation for finding the intersection of dual-satellite image pairs theoretically and experimentally, as well as its effects associated with the geometric conditions of imaging, visually and quantitatively.