Studies On The Applications Of SAR And InSAR Techniques To The Earth Science

Space borne SAR (Synthetic Aperture Radar) and InSAR (Interferometric SAR)are two kinds of new modern remote sensing space geodesy technologies, which havegot rapid development during the last 30 years. The two technologies providebrand-new tools for the 3D topographic mapping and earth surface deformationmonitoring, and play more and more important roles in earth science, such asagriculture and forestry, oceanology, topography and deformation surveying, geology,and ecology etc. Compared with America and European developed countries, studieson SAR and InSAR in China have relatively fallen behind. Until 2006, Chinese firstsmall SAR satellite was launched successfully, which spurred us to carry out morerelated researches as soon as possible so as to shorten the distance between China anddeveloped countries.Under this background, this paper introduces the principles of space borne SARimaging processing and several indexes which can reflect imaging quality. And thenilluminates the principles and limitations of InSAR and D-InSAR techniques.Subsequently, this paper focuses on the SAR imaging and the applications of SARand InSAR, and carries out some researches summarized as follows:(1) Space-borne SAR imaging processing. Imaging processing is the kernel of SARtechnique. Chapter 3 analyzes the echo signal model of point target; introducesseveral SAR imaging algorithms, illuminates the essential of range compressing andazimuth compressing during the Range-Doppler algorithm, discusses some keyproblems, such as Doppler parameters estimation, range migration correction andspeckle noise elimination in detail; and then adopts SAR raw data of Radarsat-1,ERS-1, and JERS-1 to do some imaging tests in chapter 5. Finally, we getencouraging imaging results.(2) The application of Space-borne SAR on the marine meteorology-sea windinversion by SAR image, seen in chapter 6. We first introduce the principle and threemain algorithms of ocean wind retrieval with SAR images. Then we provide the flowchart of retrieval procedures. As an example, ERS-2 SAR images covering HongKong region acquired on May 7, 2002 are used to carry out test of wind vectorretrieval. The data processing includes pre-processing of SAR image, ADC (AnalogDigital Converter) compensation, accurate calibration and speckle removal, and theapplication of classical SAR Wind Direction Algorithm for wind direction retrieval.Data collected on a buoy by the Hong Kong Observatory are then used to resolve thewind direction uncertainty. Finally, the GMF (Geophysical Model Function)-CMOD4is adopted to estimate the wind speed at the height of 10m above sea level. Comparedwith the data recorded by Hong Kong Observatory, the errors in the wind direction inthe areas of ROI1 and ROI2 are 23.71°and 7.00°, respectively, and the errors inaverage wind speed are 0.18 m/s and—0.12 m/s. The results show that betterpre-processing, together with the use of classical spectral analysis algorithm andCMOD4 model can offer high quality wind vector results.(3) Monitoring mining subsidence with two-pass D-InSAR technique in Fushun city,China. We use 6 ERS-1 and ERS-2 SAR images acquired from May 22, 1993 to Jun13, 2000 and covering whole Fushun city, and the SRTM DEM with3 arc-secondresolution to conduct two-pass differential SAR interferometry. They can form 15differential interferograms in total, but only 5 with satisfactory baseline and coherence.By investigating the 5 interferometric pairs, we obtain the subsidence rate of Fushuncity. During the data processing, we use a new modified Goldstein filtering algorithmin frequency field to filter the differential and greatly improved the interferogramquality. Finally, the case study verifies that D-InSAR technique is able to detectcm-level subsidence of the mining area.Some points of the former works deserve to be mentioned: (1) First, this paperprocesses the raw data of several satellites received by different satellite stations andcarry out related imaging tests, which provides possible answer to the uncertainproblems in InSAR data processing. (2) Second, as predicted the applications ofspace-bome SAR on the oceanology and meteorology will be one of the mostchallenging and valuable projects in the near future, meanwhile similar works inChina have not got enough attention relatively. This paper estimates the sea windvector using space-borne SAR image, and have done little improvement for theinversion algorithm, thus offered more reliable data for meteorology services. (3)Studies on mining subsidence using D-InSAR are very rare in the field of earth sciences.Therefore this paper adopts new technique-D-InSAR to investigate the miningsubsidence, and uses a brand-new modified Goldstein filtering algorithm in frequencyfield to filter the interferogram phase maps and get very good results.