Key Technology Study On POS-supported Topographic Mapping In Aerial Photogrammetry

4D products(DEM、DOM、DLG、DRG) are the fundamental data of digital city. In the times of digital photogrammetry with the primary means is 3S technology and the ultimate aim is 4D products production, it is a issue that how to make full advantages of modern aerial photogrammetric technology for the large-scale production of 4D products and for the rapid update of corresponding database. For the current production of 4D products, aerial photogrammetry is performed according to the following flow: interior orientation�'relative orientation�'absolute orientation�'stereomodel mapping. It is a mature technical means for stereo mapping of aerial photogrammetry at present, but this approach depends heavily on ground control points, which brings a lot of disadvantages for mapping. For a long time, people are in pursuit of abandoning the long-period work flow that dependence of ground control points with the following flow:aerial photography�'field control�'densification�'topographic mapping for aerial photogrammetry. With the development of sensors, it is one of the issues for airborne position and orientation system (POS) in the field of aerial photogrammetry and remote sensing in resent years. In theory, aerial photogrammetry with POS can perform direct georeferencing (DG) with the obtained image orientation parameters making aerial triangulation unnecessary, which can indeed change the work mode of topographic mapping, greatly reducing the mapping cycle, making the acquirements of geo-spatial information as well as productions and updates of 4D convenient. Owing to the existence of lever arm effect and boresight misalignment for the image orientation parameters obtained by a POS, there will be larger vertical parallax when stereo models are reconstructed. Therefore, this paper focuses on the theory and method of eliminating the systematic errors of exterior orientation parameters obatained by a POS, so as to satisfy the requirements of stereo observation for stereo model reconstructed, then is used to support automatic matching of aerial images, reaching the purposes of stereo mapping for aerial photogrammetry using the image orientation parameters directly and abandoning the operation mode of conventional digital photogrammetry with relative orientation�'densification�'absolute orientation. The main researches summarized in this dissertation are as follows: 1) Research on the method of epipolar images generation based on exterior orientation parameters obatained by a POS. According to the strict geometric relationship between the original stereo images and the epipolar images, based on the basic principle of epipolar images generated using exterior orientation parameters of images, the corresponding epipolar equations are deduced. The twelve elements of exterior orientation obtained by a POS are used directly to establish the epipolar equations. which changes the traditional operation mode for the generation of epipolar equations must matching more than five corresponding image points first to calculate the elements of relative orientation.2) Research on the vertical parallax of stereo model reconstructed using exterior orientation parameters obtained by a POS, and the accuracy effects of errors containing in exterior orientation parameters to vertical parallax. Firstly, the formula of vertical parallax calculated using exterior orientation parameters is given. Then, based on the theory of error propagation law, the theoretical accuracy mathematical model of exterior orientation elements to vertical parallax is proposed. Finally, the empirical accuracy of vertical parallax is calculated and the effects of errors containing in exterior orientation parameters to vertical parallax are analyzed.3) Research on the method of systematic errors elimination for exterior orientation parameters obtained by a POS. Comparison the vertical parallaxes calculated using exterior orientation parameters obtained by different means. The different kinds of the compensative models for systematic error of POS are used to eliminate the effects of systematic errors to vertical parallax, so as to satisfy the requirements of stereo observation. Then the more exact elements of exterior orientation are recalculated according to the compensative parameters and the original exterior orientation parameters obtained by a POS.4) Research on the image matching based on epipolar constraint established by exterior orientation parameters obtained by a POS. According to the accuracy of epipolar itself, the vertical parallax of corresponding image points can be more accurately predicted, for the horizontal parallax, the initial location of candidate matching points can be more accurately determined based on the exterior orientation elements and the average elevation in the region covered by the images. Therefore, the initial location of candidate matching points can be more accurately predicted based on the exterior orientation elements and the epipolar constraint, which can further reduce the searching range to ensure the corresponding image points within the searching scope, achieving the purpose that fast and reliable image matching.5) Research on the method of DOM generation supported by exterior orientation parameters obtained by a POS. The corresponding image points obtained by image matching supported by POS data are used to calculate the three-dimensional coordinates in object space and thus generate the DEM. Then the DOMs are generated by differential rectification for each image according to the generated DEM and image exterior orientation elements...