Research On Coherent Target Interferometry And Its Applications Of Surface Subsidence In Beijing

InSAR is a new technology of radar remote sensing which developed in recentdecades.It has many advantages in DEM reconstruction and surface subsidencemonitoring compared with traditional methods such as rapid access to images,largearea of continuous monitoring,capacity of all-weather and all-time.So it has becomeone of the most potential technologies in the area of microwave remote sensing.The reliability of results calculated by traditional D-InSAR is poor because itonly uses two images to study the single deformation and it lack of redundantobservations.For the long-term slow surface deformation monitoring,the singlediscrete observations by D-InSAR cannot be connected due to the limit of baselineand observation cycle.So the development and the evolution of deformation in thestudy area cannot be obtained.The coherent target interferometry method uses highcoherent points to interfere to weakened the coherence problem caused by spacebaseline.And the accuracy of deformation calculation can be further improved.Firstly,this paper introduced the fundamental and basic procedure of D-InSARand obtained a deformation map by two-pass method.Then the main source of errorsin D-InSAR was analysed,including registration error,baseline error and atmosphereerror.Secondly,four D-InSAR methods based on coherent target were introduced indetail.In particular,the SBAS-InSAR technology was studied systematically.The SBAS-InSAR method firstly combines the SAR data on the basis of theirspace and time baseline.All the SLC data need to be registered with one publicreference image.Then we choose the high coherent points based on a certaincriteria.The time series deformation in each set can be obtained by the leastsquares(LS) method and the problem of the overall normal equation rank deficient canbe solved by singular value decomposition(SVD).So we can obtain the time seriesdeformation which covers the whole observation time by combining the sets of smallbaseline.Finally,we used SBAS-InSAR technology to study the land subsidence inBeijing.The map of deformation and deformation rate were obtained by52 Envisat-ASAR images acquisitioned from2003-6-18to2010-8-25and the resultswere analysed in detail.We can see the central area of Beijing city is relatively stable, and there areseveral obvious subsidence zone in the north east from the map of deformationrate.The surface deformation of Beijing has its obvious characteristics.Besides theexploitation of groundwater, the rise of various development zones and build factories,has been becoming the key factor of urban land subsidence.The city groundsubsidence,is not only a geological problem,but also a problem related to theeconomic development of the social.