Height Reconstruction Of Urban Buildings Based On Multi-baseline InSAR Technology

Interferometric Synthetic Aperture Radar(InSAR)can be used to recover elevation direction phase from multi-baseline SAR data.InSAR technology has the advantages of high efficiency,low cost and weather-proof.A range of high-resolution SAR data such as Terra SARX and Cosmo/Skymed also make it possible to obtain more accurate surface elevations through multi-baseline InSAR technology.In addition,InSAR technology based city building height inversion has important application prospects for urban planning,urban management,resilient city,three-dimensional urban real scene construction and other municipal fields,as well as disaster prevention and control fields such as disaster assessment,disaster prevention and reduction.InSAR technology is mainly used to solve terrain and shape variables.In addition to atmospheric delay and other influences,the phase unwrapping problem is more difficult to solve in the process of recovering the elevation residual phase corresponding to terrain factors.When the elevation difference between pixels increases abruptly,it will cause the phase ambiguity problem of the phase difference between adjacent pixels,which breaks the phase continuity assumption of conventional unwrapping algorithm and makes it difficult to untangle accurately,causing trouble for the elevation recovery of target region through InSAR technology.Therefore,this paper mainly realizes the inversion of building height by solving the unwrapping problem of the phase discontinuity of elevation residuals between pixels in the multi-baseline InSAR technology process.The main research content and innovation of this paper include the following aspects:(1)The research progress of four classical building elevation inversion methods based on SAR data is summarized.The reasons of InSAR technology for elevation reconstruction are explained,and the current research status of the phase unwrapping problem faced by the selected method is summarized.The basic principle of InSAR technology for building height inversion,the basic theory of phase unwrapping algorithm and the data processing flow are introduced.(2)The dense phase fringe of elevation residuals in long baseline interference data leads to serious phase jump,which is not conducive to the application of unwrapping algorithm.In this paper,Integer Interferometric Combination(IIC)is adopted to combine long baseline data into short baseline data.The setting method of baseline threshold is improved,which makes unwrapping easy and reduces the height resolution accuracy by reducing the base line too short,and obtains the building height results with higher accuracy than before the combination improvement.(3)The shortening of the baseline will increase the elevation ambiguity number,which will reduce the elevation estimation accuracy.Another idea of this paper is to improve the unwrapping ability of the unwrapping algorithm to achieve reliable unwrapping of long baseline data.By improving the traditional unwrapping network method,the unwrapping algorithm based on the finite difference connection network is realized,which can unwrap the long baseline data with many phase jumps.The effectiveness of the algorithm is proved by comparing the simulated and real data with the traditional Minimum Cost Flow(MCF)algorithm.The results of building height calculation with higher precision in the target area are obtained.