Three-Dimensional Positioning Using SPOT Stereostrips with Sparse Control

Abstract

This paper describes an experiment for a proposed scheme using on­ board satellite data to perform three-dimensional positioning for a pair of SPOT stereostrips. Based on the sampling geometry of French SPOT satellite images, we first adjusted the on-board parameters by incorporating a small number of ground control points (GCPs). 1ben a procedure for three-dimensional modeling was per­ formed as follows. The central features of the proposed scheme are: (l) use of on­ board data to initialize orbit parameters and attitude data for the satellite; (2) cor­ rection of on-board parameters with low order polynomials; (3) use of reverse transformation to check the collinear relationship between object space and image space for the GCPs; (4) adjustment of attitude data for the satellite to minimize the error in terms of the GCP collinearity; and (5) space intersection. Experimental results indicate that, for a SPOT panchromatic stereostrip with a 0.6 base-to-height ratio and a 45 km by 280 km stereo model area, the root-mean-square-error for 3­ D positioning is less than 8 m in each direction when only 4 GCPs are used. Three-dimensional positioning for object points is an important task in the field of civil engineering when geometrical data processing is needed. Terrain data are often required in the planning, design, and construction stages of various transportation and hydraulic engineering projects (Epps and Corey 1990; Jones et al. 1990). Three-dimensional terrain information is also required for geometrical correction (Wiesel 1985) and terrain-dependent radiometric correction (Colby 1991) of remotely sensed images. Three-di­ mensional terrain data may be obtained from ground surveying with the ex­ pense of intensive labor, but a labor-saving approach is possible when pho­ tograrnmetric techniques are used. A higher efficiency may be anticipated by the use of a digital approach to automate the working procedure. Nowadays, because the spatial resolution of satellite images is significantly improved and stereoscopic sampling is available, the efficient extraction of 3-D terrain data becomes possible. Currently, French SPOT satellites have the highest tem­ poral and spatial resolutions among the available earth resource satellites. In addition, due to their side looking characteristics, SPOT satellites may pro­ vide cross-track stereo pairs. Thus, SPOT images have high potential for the extraction of 3-D terrain information. From the photograrnmetric point of view, collinearity condition equations are generally used in 3-D positioning for SPOT stereo pairs. Based on the equations, a bundle adjustment may be applied to model the satellite orien­ tation and the 3-D ground coordinates for a pair of conjugate image points (Konecny et al. 1987; Gugan and Dowman 1988). This approach may reach subpixel accuracy. However, a large number of ground control points (GCPs)