Automatically Building Of DSM And DOM For ZY-3Satellite

ZY-3satellite was launched from Taiyuan satellite station at11:17, January9th,2012,with three-line-array panchromatic camera and one multiple spectral camera configured. Inthis paper, three-line-array images are processed, digital surface model and digital orthophotomap is built by rational function model with RPC parameters following with three-line-arrayimages, with neither control points nor digital elevation model. It is useful when in emergency,control points is difficult to get, or other basical geo-products is also blank.The contrast of ZY-3satellite three-line-array image is bad, auto-enhancement is carriedon with PS before image processing. Feature points from forward and backward images ofZY-3are extracted by improved Harris feature extraction algorithm based on Gauss difference.Details of image is enhanced after Gauss difference, then Harris algorithm is used, during thewhole process of feature extraction, twice of local extreme detecting can avoid redundantfeature points. Two direction feature matching based on correlation coefficient are carried onafter feature extraction between forward and backward images, slope constraint can get rid ofthe wrong matching points because the trend of their line between each other is more differentfrom others. Then initial parallax image is established with homogeneous points after featurematching, belief propagation algorithm is used to optimize the initial parallax image, parallaxenergy function of every pixel is the minimum, the best correspondence of all pixels inoverlap area between forward and backward images.After feature extraction, feature matching and global matching, rational function modelsof homogeneous pixel in forward and backward images are built with their RPC parameters,error equation can be obtained by linearization of RFMs above, true3D coordinates in groundcoordinate can be calculated by least square parameter adjustment, then dense point cloud canbe obtained, DSM is also built. A blank image is established before ortho-rectification to nadirimage, real3D coordinates from overlap between forward and backward images will beassigned to corresponding location, then coordinates of other pixels is interpolated bycoordinate which already had. Location of the pixel of blank image in nadir image iscalculated by RFM of nadir, the pixel light-value is obtained by resample of bilinearinterpolation. In the last part of this paper, precision assessment is carried on, the result showsthat the plane precision of DOM from ZY-3nadir image established by this method can reachmore advanced level.Experiment proved that without control points and DEM, feature extraction, featurematching, global matching based on belief propagation algorithm are carried on forward andbackward images of ZY-3. Then DSM can be obtained by parameter adjustment from RFM offorward and backward RPC parameters. Finally, nadir image of ZY-3is ortho-rectified withindirect RFM, the plane precision of DOM above can reach advanced level in the samecondition.