A unified solution for digital terrain model and orthoimage generation from SPOT stereopairs

An original scheme to automatically generate digital terrain models (DTMs) and orthoimages from SPOT stereopairs in a unified way is presented. In addition to modeling the time-dependent orientation parameters, an algorithm is developed to generate the epipolar stereomate incorporating an initial DTM. The refining of the DTM is then accomplished by performing least-squares template matching along each conjugate epipolar line pair, space intersection, and grid value interpolation. Recursively, the epipolar stereomate is regenerated according to the refined DTM. The procedure is repeated until the disparities between the two stereomate images are small enough. The DTM generated illustrates the apparent surface. It is more correct to use this apparent DTM than the one depicting the ground surface for the geometric correction for remotely sensed data. Both images of the final epipolar stereomate are actually orthoimages because they are geometrically identical and georeferenced. Experimental results indicate that the orthoimages reach an accuracy up to 2/3 pixel