The High-resolution Synthetic Aperture Radar Interferometry (INSAR) Technique And Its Applications Research

Interferometry Synthetic Aperture Radar(InSAR) is an advanced space observation technique. It is the synthesis of conventional SAR techniques and interferemetry techniques that have been developed over several decades. It relies on the processing of two SAR images of the same portion of the Earth's surface obtained either from two displaced passes of the SAR antenna at different times (repeat-pass interferometry), or from two antennas placed on the same platform and separated perpendicularly to the flight path (single-pass SAR interferometry). The 3D information of the ground and the deformation of the elevation can be extracted by according to the interference phase information of the two SAR images and the high accurate terrain information can be generated all over the world. It has the features of fine resolution mapping, working under any weather condition, imaging in daylight or at night, wide mapping range and with lots of applications. The difference InSAR(D-InSAR) is developed based on InSAR. It can monitor the tiny variation on the surface of the land and ice on the earth. It also can obtain high accurate and high credible deformation of the earth's surface. InSAR and D-InSAR can be used to study the change of the unreachable areas before such as the glacier and the ice barrier. And also this technology can explore the Earth's surface hazard deformation such as earthquake, volcano, coast, flood, minitary and so on. So it has been the studying hotspot in the satellite remote sensing field.The development history, application actuality, geometry imaging principle and data processing procedure of InSAR are introduced. The principles and algorithms of the key technologies including registration of SAR images, the flat earth effect removal, filtering of the interferogram and phase unwrapping are deeply discussed and analyzed. The application of the InSAR and D-InSAR in the Earth science field are studied and the actual examples are provided.The registration of the two SAR complex images used for interferometry must be performed. To obtain better measuring results, a method is proposed to improve the registration accuracy progressively for InSAR complex image. The procedure includes calculating the approximate offsets by using EnView software, pixel level's coarse match and sub-pixel level's precise co-registration. The primary matching algorithm based polygon structure and edge extraction enhances matching rate greatly. Considering that the presented algorithms are based on the altitude images and ignore the integration, the algorithm by using global relaxation matching on account of the phase is proposed in the last matching step to reduce the matching errors and improve matching precision. The experiment shows the nicer validity of this algorithm.The phase information of the interferogram generated after registration includes terrains information and flat earth effect information. To acquire accurate terrain information, the latter must be removed. Aimed at the difficulty to get parameters and the low precision of the common methods, a high accurate algorithm to obtain a precision result based on frequency shift and linear interpolation technology was proposed in this paper. Taking full advantage of the frequency shift method, this algorithm can improve the resolution of the frequency shift through linear interpolation. The actual data shows the feasibility and validity of the algorithm in the processing.There is multifarious noise in the interferogram with the anisotropy characteristic. The conventional methods eliminate the noise with the rectangle filtering window. Thus the phase information is confused and the fringe information maybe damaged. Aimed at the stripe's anisotropic characteristic, a method for InSAR interferogram filtering based on the center lines of interference-stripes is proposed. It first extracts the center of interference-stripes quickly by using CNN(Cellular neural networks) algorithm for it's parallel feature to process data. According to the center lines the contoured filtering window is obtained. The InSAR interference phase images have 2Ï€jumping lines. So finally the sine or cosine filtering combined with the equal phase lines filtering window is performed which can remove the noise of the InSAR phase images while avoiding damaging the phase distributing. The filtering of two fact interference phase images is implemented with this method. The experiment results with good visual feature, little residue and strong image edges holding ability show that this method is efficient.There are two main types of phase unwrapping algorithms: based on path tracing and based on the least square method. The two methods hardly give attention to both aspects of precision and speed. A layering phase wrapping method based on Delaunay triangulation net minimum cost flow (MCF) algorithm is proposed. The interferogram is divided into high quality phase areas with few residues and low quality phase areas with lots of residues. Considering the irregularity of the residue distributing and the maturity of the minimum cost flow algorithm, the MCF based on Delaunay subdivision is used to unwrap the phases in the high quality components. The region growing unwrapping algorithm is used to unwrap the phases in the low quality components starting from the points in the high quality areas which has been unwrapped with MCF. The precision and the speed of the unwrapping are improved at the same time.By using the algorithms proposed in this paper and according to the SAR data from ERS-1/2, the digital elevation model of the Kashi area is generated by using InSAR technology. According the ASAR data from ENVISAT, the difference interferogram reflecting the Earth surface deformation (caused by the earthquake happened on Dec.26, 2003) image of the Bam area in Iran is generated by using D-InSAR technology.