Study on satellite radar interferometry

最近对卫星雷达干涉测量法的研究表明，它有能力绘制三维地形图、地震或南极冰盖流动造成的位移场。然而，它指出，为了获得精细的测量，需要厘米级精度的精确基线和水蒸气的距离延迟的影响是不可忽略的。这项研究的目的是通过使用角反射器的实验和利用日本地球资源卫星对L波段合成孔径雷达数据进行干涉分析，调查卫星雷达干涉测量的能力。对于具有大雷达反射的CR，证明了从具有故意6 cm和10 cm位移的CR检测到1 cm精度的位移。对于一般的地表，在干涉图上观察到了局部的和大的相位变化，其等效位移超过1厘米。可能的原因是表面条件的时间变化。为了提高大面积干涉相位测量的精度，提出了干涉仪基线的估计方法。利用气象台站的气压、温度和水汽压观测数据和数字高程模型，研究了大气中水汽引起的距离延迟的制图方法。分析表明，由于研究区存在较大的地形高度变化，且某些干涉组合来自不同的季节（夏季和冬季），水汽对雷达干涉图的影响很大。

Recent studies on satellite radar interferometry have demonstrated the capability of mapping of 3-D terrain, displacement fields caused by earthquakes or ice sheet flow in the Antarctica. However, it is pointed out that in order to derive fine measurements, accurate baselines with cm order accuracy are required and that influences of water vapor on range delays are not negligible. An objective of this study is to investigate a capability of satellite radar interferometry through experiments using corner reflectors (CRs) and interferometric analysis of L-band synthetic aperture radar data with the Japanese Earth Resources Satellite. As for a CR that has a large radar reflection, detection of a displacement of l-cm accuracy was demonstrated from CRs with intentional 6-cm and 10-cm displacement. As for general land surfaces, local and large phase variations whose equivalent displacement is more than 1-cm were observed over interferograms. Possible reason is temporal change of surface conditions. To improve an accuracy of interferometric phase measurement over large areas, the method to estimate interferometer baseline was advanced. The method to map range delays due to water vapor in the atmosphere was developed using observation data (Air presser, temperature and water vapor presser) at meteorological observatories and digital elevation model. Analysis shows water vapor has a great influence on the radar interferograms, because there exists a large terrain altitude change over the study area and some interferometric combinations are from different seasons (i.e. summer and winter).