期刊名称：ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
印刷版ISSN：2194-9042
电子版ISSN：2194-9050
出版年度：2005
卷号：XXXVI-8/W27
出版社：Copernicus Publications
摘要：Orthoimages are very important geospatial datasets, forming the database for a great variety of applications. So far, orthoimages are generated from aerial photographs by differential rectification to correct the effects of relief displacements. Digital Terrain Models (DTM) describe only the topographic surface but ignore trees, man-made objects, etc. Therefore, the effect of leaning buildings or bent bridges appears, especially in urban areas. Expensive Digital Surface Models (DSM) describe the entire surface including the mentioned objects. This enables the generation of orthoimages of a high quality which are called "True Orthoimage". Now, recent developments of optoelectronic line-scanning cameras like HRSC or ADS 40 allow for a totally new approach for orthoimage generation. The nadir-looking channels of these cameras provide image data in parallel projection along the flight line, and in central perspectives across. If a scene is imaged twice in flight lines perpendicular to each other, the first image strip provides correct ground coordinates of any object in one direction, the second image strip in the other direction. The new approach takes advantage of these particular geometric properties by combining the correct ground coordinates of each point. Thus, the generation of a true orthoimage becomes possible without height information. Due to the mixed projections of pushbroom sensor imagery, the relief displacements occur only in one direction. Thus, occluded areas are significantly smaller than in conventional aerial photo- graphs. Moreover, the new approach takes advantage of the particular pattern of certain urban areas, to fill up remaining gaps with image information only from the participated image strips
