Building Height Extraction Based On High Resolution Twin-satellite Formation SAR Images

Currently,urbanization process is rapidly accelerating,and cities are experiencing fast development and expansion in the world.Three-dimensional building information,as a part of the foundation of urban geographic environment information,provides information support for the analysis of urban spatial structure,spatial evolution mode,and related economic and population data estimation.Thus it is served as the basic data for the evaluation of urban development status and other important applications.Using SAR interferometry can obtain the 3D information of urban area,but the elevation extraction of buildings remains to be a relatively difficult problem because of phase unwrapping and overlay.With the rapid development of radar remote sensing technology,the level of ground observation of SAR is constantly improving.High-resolution SAR data stack can provide more details of urban building targets,which is conducive to height extraction in urban areas;while a series of new SAR sensors continue to rise,the trendency exists in multi-satellite networking in combination with different flight modes,and image acqusition modes.With these multi-satellite formation or twin satellite formation,different orbit settings as well as imaging modes can provide innovative SAR datasets with new characteristics.Some of the characteristics in those innotative SAR data stacks demonstrate great potential in promoting the ability of InSAR-based height extraction in urban areas.Hence,it is very important and necessary to explore the application prospect of these new SAR datasets in urban building elevation extraction.In this thesie,TerraSAR-X and TanDEM-X twin satellite formation is chosen as an example to study the application of innovative SAR data obtained from multi-satellite formation.The research focused on three types of data,and on the basis of summarizing the existing methods of urban building elevation extraction,a comprehensive study is conducted on urban building elevation extraction based on the forementioned three kinds of high-resolution twin satellite formation flight mode SAR datastack.Based on the single orbit with single satellite SAR datastacks,i.e.the repeated orbit SAR stacks,the thesis utilize the permanent scatterer interferometry(PSI)and SAR tomography technology to extract the elevation information of buildings,and the sub meter resolution Tan DEM-X staring spotlight SAR data stack is used to carry out experiments in Wuhan,which have achieved good results.By comparing the experimental results of elevation extraction obtained by the two methods,the advantages and disadvantages of the two methods as well as their appropriate application context in the aspect of elevation extraction of urban buildings are analyzed.Based on the single orbit with twin satellite SAR datastack,namely the pursuit mono-static SAR datastacks,the thesis first introduces the special properties and related research of this new type of SAR image sets.Compared with the conventional SAR stacks,the extremely short temporal baseline interferometric pairs in these datasets can extract more accurate terrain phase information.Therefore,those image pairs are naturally proposed to be directly incorporated into the processing flow of standard PSI.However,the standard PSI can not make full use of the characteristics of the very extremely short temporal baseline and may cause some potential numerical problems.In this context,this thesis first proposes a modified PSI method,which avoids the numerical problems that may occur when the standard PSI method and it is successfully applied to the field of urban building elevation extraction.The field experiments of standard PSI and modified PSI are carried out by using the Pursuit Monostatic SAR stacks in Guangzhou.The results show that compared with the standard PSI method,the modified PSI method demonstrate a greater improvement in the extraction ability of urban building elevation information,and successfully exhibits the advantages and potential of Pursuit Monostatic SAR stacks in the extraction of urban building elevation Their application boundaries is therefore broadened.Based on the dual orbit and twin satellite SAR stacks,taking the cross-track image image sets as an example,the thesis analyzes their advantages in extracting the three-dimensional information of urban buildings from different tracks and complementing each other,which is conducive to extracting the complete surface information of buildings.However,the elevation extraction of buildings based on multi-orbit SAR data stacks often depends on the 3D point cloud information generated from individually processed SAR image set,and the reference elevation of different point clouds is often inconsistent,which will lead to the difference of the elevation of the homonymous PS pairs,which coming from the different point clouds and are conresponding to the same real world target.Based on the Geometric Fusion model,a geometric parameter solution is implemented based on the appropriate homonymous points and the least squares iteration,the aim is to estimate the three-dimensional offset between the homonymous points and their real positions between data stacks from different orbit,as well as to correct the elevation deviation and to implement the multi-data fusion.In this thesis,cross-track SAR data stacks of different resolution are used in Las Vegas and Shanghai to carry out field experiments,and good data fusion results are achieved.The high-resolution twin satellite formation SAR data stacks can improve the ability of urban building elevation extraction in many aspects,thus it can be considered to be of great value in urban building elevation extraction.With the twin-satellite formation is becoming more and more mainstream flight mode for current and upcoming SAR sensors,and the data sources becoming more and more abundant,the application prospect of this type of data in this or other fields deserves further in-depth study.