Research On Technologies Of Accurate Positioning With SAR Images

The economy and society in China develop steadily and fleetly in recent years. It demandsto improve the up-to-data efficiency and the precision of fundamental geography information.Positioning and three dimensional (3D) information extraction from Synthetic Aperture Radar(SAR) images, is an important approaches for deriving fundamental geography information. Ithas the advantages of all time, all weather, high efficiency and high resolution. However, thereare many technology difficulties in positioning and3D information extraction from SAR images.In order to improve the capability of positioning and3D information extraction, positioningmethods with stereo SAR images as well as single SAR image without Ground Control Point(GCP) were studied. Positioning and3D information extraction from multi-baseline or MultipleInput Multiple Output (MIMO) Interferometric SAR (InSAR) images, as well as matching ofSAR images were researched. Experiments using high resolution airborne SAR images weredone. The main work and innovations of this thesis are listed as follows:1. Comprehensive review of the present situation of positioning and3D informationextraction from SAR images was done. The main problems that restrict the utility of3Dinformation extraction from SAR images were analyzed. With the geometry and radiationcharacter analysis of SAR images, the confusing concepts of speckle and noise, image resolutionand pixel spacing were analyzed. Geometrical imaging models of SAR images, positioning withstereo SAR images, positioning with single SAR image, and the fundamental principles ofInSAR images for positioning and3D information extraction were systematically discussed.2. An accurate positioning scheme based on Range-Doppler (R-D) model was designed forhigh resolution airborne squint stereo SAR images. It calibrates the close range and the Dopplerfrequency as overcomes the difficulty in solving the orientation parameters. Airborne SARimages positioning with1meter level error was realized.3. A positioning scheme for single squint SAR image based on Digital Elevation Model(DEM) without GCP was proposed. It simulates SAR image with DEM, and extracts GCPs bymatching the simulated SAR image and the actual squint SAR image, and then, the orientationparameters with squint R-D model can be calculated to complete single SAR image positioningsupported by DEM. For the matching of simulated SAR image and actual SAR image, two kindsof matching strategies that respectively take simulated SAR image or actual SAR image asreference were discussed. The conclusion is that the matching with simulated SAR image asreference is better. A series of positioning experiments with single SAR image were carried outusing high resolution airborne SAR image, Shuttle Radar Topography Mission (SRTM) DEM or earth model equations. The errors of positioning with each scheme were statistically analyzed, asverified the proposed method.4. A scheme with differential filter for positioning and3D information extraction fromMIMO InSAR images was proposed. The interferograms were simulated with direct algorithmand indirect algorithm. The experiments of positioning and3D information extraction fromsingle baseline InSAR were carried out with simulated different baseline interferograms. Itverified the fact that the shorter baseline InSAR has lower accuracy and strong solvability, whilethe longer baseline InSAR has the opposite feature. Multi-baseline InSAR can utilize variousbaseline data. The scheme with differential filtering and the one with Chinese RemainderTheorem (CRT) for multi-baseline InSAR were designed. The advantages of higher precisionand solvability in multi-baseline InSAR were verified through the experiments with simulateddata. The scheme with differential filter for positioning and3D information extraction fromMIMO InSAR images was proposed. The interferogram with lowest frequency was processedfirstly by filtering and phase unwrapping, and then the interferogram with higher frequency wasprocessed by difference, filtering and phase unwrapping one by one, so as to finish accurateheight deriving. MIMO InSAR interferograms simulation and processing experiments werecarried out, as validated the proposed scheme.5. An automatic matching for SAR images with multi-look and bilaterial sequence byprediction of point’s position with Position and Orientation System (POS) and SRTM DEM datawas proposed. This method predicts point position using POS and SRTM DEM data, enhancesimages by extracting line features, and proceeds with multi-look and bilaterial automaticmatching. It can decrease the effect of the larger relative geometric and radiation distortion. Itcan get better matching results, as was verified by varied different resolution images.6. The research achievements were integrated, as including stereo SAR images positioning,single SAR image positioning, InSAR images positioning and3D information extraction, SARimage matching and so on. And the software for SAR image positioning and3D informationextraction was built. Experiments of positioning, extraction of3D information and matching ofSAR images were done with airborne SAR images acquired by Chinese academy of surveyingand mapping and with simulated SAR images, as validated the research achievements.The research achievements in accurate positioning and3D information extraction from SARimages will improve the positioning accuracy of SAR images in our country. It can promote thedevelopment of3D information extraction from SAR images and the application of SAR interrain surveying and mapping.