摘要
GPS数据用于改正InSAR中大气延迟误差的方法受GPS站点密度的限制,只利用有限的几个站点所观测到的大气数据来生成干涉图的大气改正图,往往达不到很好的效果.本文研究利用GPS与MODIS数据的联合使用来生成大气改正图,首先用GPS数据对MODIS水汽产品进行分块校准,并且对MODIS水汽数据进行了空间结构函数分析,得到研究区域内水汽场的空间分布规律.然后把这种区域水汽场的空间分布信息结合到Kriging内插法中生成更为合理的水汽图.通过上海地区ENVISAT ASAR数据的实验发现,这种加以改正的GPS和MODIS数据联合改正法不仅可以对长波大气信号有明显的消弱,还能消弱一些短波的大气信号,特别是一些幅度较强的短波信号;经过GPS+MODIS算法改正后,短波信号占优和长波信号占优的两幅差分大气延迟图的整体RMS分别降低了32.74%和38.82%,去除幅度较大.与GPS+ATM(大气传输模型)算法比较,我们发现,在上海地区有限的数据条件下(即研究区域内只有6个GPS点),GPS+MODIS法在大气去除效果或者说大气信号重现能力方面优于GPS+ATM算法.GPS+MODIS算法在捕获短波大气信号方面要比GPS+ATM更有优势,因此也可以改正短波大气误差.
It is usually believed that the sparse spatial resolution of GPS stations is a main limitation factor for improving correction accuracy when we only use GPS-ZWD data to mitigate atmospheric effect in repeat-pass InSAR measurement. In this paper, a method is investigated to generate water vapor delay map using a few GPS stations and MODIS near-infrared water vapor products, which is used to correct atmospheric effect in interferogram. Firstly, a patch-wise calibration method which partitions the MODIS product as several patches based on the location of GPS stations is adopted to correct the scale error in MODIS water vapor data of every patch with corresponding GPS-ZWD, then the calibrated MODIS data is analyzed using spatial structure function, and spatial distribution law of water vapor in the area of interest is achieved. Finally, this kind of spatial distribution information of water vapor is incorporated into the Kriging interpolator to generate much reasonable water vapor map. The experimental results from two interferograms of Shanghai ASAR data show that the atmospheric water vapor difference map from the GPS＋MODIS method can remove not only part of long-wavelength atmospheric components significantly but also some short-wavelength signal, especially ones with strong amplitude. After applying GPS＋MODIS method, the global root mean square （rms） atmospheric phase fluctuations of the interferograms dominated respectively by short- and long-wavelength signals decrease significantly by a2.74% and 38. 82% respectively. Comparing with GPS＋ ATM algorithm, we found, the GPS＋ MODIS method is better than GPS＋ATM algorithm to remove atmospheric effect, and it hold stronger ability to reproduce atmospheric signal, especially short-wavelength signal, than GPS＋ATM algorithm under existing data condition of Shanghai research area （only six GPS station）.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2009年第6期1457-1464,共8页
Chinese Journal of Geophysics
基金
国家科技支撑计划(2006BAC01B03-01-03)
国家自然科学基金(40574007)资助
