Study On Transform Compression Code For CCD Aerospace Photogrammetric Image Date

Based on the requirement of the aerospace photogrametric camera with three-line array CCD, the purpose of this dissertation is to study transform compression code about aerospace photogrametric data.The mathematic model for line-array CCD photogrametric imaging is constructed according to the principle of the three-line array CCD photogrametric camera., and also various factors resulting in the geometric error are analyzed. Most coding algorithms are characterized by changing the energy distributing in the coding image, the method used to compute the geometric error of correlative points was proposed by the correlation coefficient operations. In addition the method on sub-pixel computation was given.The efficiency problem of removing correlation and energy compression in orthogonal transform coding image is studied and discussed. First, with the first -order Markov process used as correlation computation model, the various orthogonal transforms are considered with efficiency of both removing correlation and energy compression. Secondly, step signal considered as the model of image edge signals is used to research compression efficiency of image energy. Last, the optimal orthogonal transform is defined as discrete cosine transform (DCT).The algorithm of adaptive DCT compression code for remote sensing image is proposed. First, different active remote sensing images are encoded and decoded by JPEG standard basic algorithm. In addition both peak value signal noise ratio and geometric error of correlative points are considered as evaluated criterion to confirm the dynamic range of quality factor and code rate in JPEG basic algorithm without any degradation of the image geometric fidelity. Further, because a variety of image edge are characterized by different AC coefficient energy distributing, the quality factor relative to different quantization step length is used to be adjusted different image edges so that improving code rate with the remaining fidelity. And then new algorithm of adaptive quantization AC coefficients with edge classification is studied.Finally, the simulation experiments are showed that compared with JPEG algorithm the new method reduces 15.54% of the code rate and saves 8.3% of operation time.The DCT compression coding system with vector quantization has been studied here. First, based on vector theory the fast search method for vector quantization coding is discussed. Also a new codebook structure of fast classification search for codeword is proposed. In addition according to the characterization of the uniform area in the remote sensing photogrammetric image, the adaptive DCT coding system with uniform classification is brought forward. Then the test images are used to proceed simulation experiment. With comparison with JPEG and adaptive DCT coding the hybrid method is proven to highly improve the correlation geometric precision and coding efficiency. Finally the hybrid code algorithm is used to encode practice image photographed by the three-line arrays CCD photogrammetric camera. The experiment results show that the hybrid method is characterized by lower code rate and the decoding images represent high image quality.