A study on the maximum and minimum detectable deformation gradients resolved by InSAR

Abstract

The phase noise in a SAR interferogram is the function of both interferometric coherence and multilook number. In InSAR, except the hardware limitation, the maximum and minimum detectable deformation gradients are directly affected by interferometric phase noise. In addition, multilook operation will alter the size of pixels and thus the maximum and minimum detectable deformation gradients. This paper investigates the relationship among the maximum/minimum detectable deformation gradient, the multilook number and the coherence, and establishes the empirical function models of the maximum/minimum detectable deformation gradients for multilook number 1, 5 and 20. Experimental results with Envisat ASAR data over the area of Bam, Iran show that the new models can accurately judge whether a given ground deformation can be resolved by InSAR. Comparing with the model incorporating only coherence information, the new model is more accurate and comprehensive. InSAR干涉图中的相位噪声是相干性和视数的函数.InSAR能检测的地表最大最小形变梯度,除了受到InSAR硬件的限制外,还直接受到InSAR干涉图中噪声强弱的影响.此外,由于多视处理会改变像元的大小,也会引起可检测的最大最小形变梯度显著变化.本文研究了 InSAR可检测的地表最大最小形变梯度与相干性和视数的关系,并建立了视数为1、5和20时(ERS和ENVISAT常采用的多视数)InSAR可检测的最大最小形变梯度的经验函数模型.最后,本文用伊朗Bam地区的Enivsat ASAR数据进行了试验,结果表明该模型能够准确地判别不同视数和相干性情况下地表变形能否被InSAR技术所检测.与Baran只考虑了相干性的模型相比,本文的模型适用范围更广.