Generation of Orthorectificated Image Patches from Multiple Images

Orthoimages can be used for several purposes. One of them is used them as control information, instead of artificial targets, to determine the exterior orientation of new aerial images. For such a purpose, the image displacements on aerial photos, usually tilted photographs, caused by topographic relief (including the relief of topographic objects) should be removed. In that case the correct geometrical and radiometric information can be obtained from those orthoimages and provided for control information. That means “true” orthoimages should be generated. However the generation of “true” orthoimahes needs the accurate height information of terrain areas and the acquisition of accurate height information are always time-consuming and labour-intensive. Therefore this paper will try to propose a method to efficientally generate the orthorectificated image patches as controls for aerotrianguation. This proposed methodology will generate orthoimage patches from multiple aerial images without detailed terrain height information. A concept of floating plane, similar to the concept of floating mark, will be presented in this paper to produce several candidate sets of orthoimages for a terrain area at some height range. Each candidate set consists of several possible related orthoimage patches of a terrain area from multiple images at some height. Subsequently, a procedure will be developed to decide an optimal set from those candidate sets for this terrain area. A unique orthorectified image patch of this terrain area will be fused from this optimal set. The relevant assessment of accuracy will be also discussed and conducted in this paper. Finally, experiments prove the good geometric accuracy of proposed methodology.