The geometric relationships between the SPOT stereo images and the ground points can be approximately described by simplified polynomials in place of collinearity equations.

Because the SPOT image is obtained by the so-called "push broom" scanning principle, the position of projecting centers is a time-dependent function. Using rigorous collinearity equations to solve space intersection problems is much more difficult than that of the aerial photography. Kratky proposed the polynomial mapping functions (PMFs) to solve the problem of real-time positioning in analytical plotter. Here, we attempt to apply them to the matching problems of digital SPOT stereo images.

The PMFs in this research have three major applications?First, the polynomial

functions for the image-to-image relationships are used to define geometric constraints in image space. Second, the image-to-object PMFs are used to perform space intersection to get the ground coordinates. Finally, the object-to-image PMFs are used to project grid points of the DTM up ward to SPOT images for orthoimage generation.

The matching of SPOT stereo panchromatic images using PMFs can achieve an accuracy of 10 m in elevation. Moreover, PMFs can be used to derive a very good approximation of the epipolar lines, which can be used to reduce the search space from 2-D to 1-D and also increase the success rate of the image matching.

Keywords:

*M. Sc., Department of Surveying Engineering, National Cheng Kung University

**Professor, Department of Surveying Engineering & Institute of Photogrammetry, Cheng Kung University

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