A New Baseline Linear Combination Algorithm for Generating Urban Digital Elevation Models With Multitemporal InSAR Observations

The lack of high-resolution digital elevation model (DEM) data presents one major limitation for deformation mapping using synthetic aperture radar interferometry (InSAR) techniques with high-spatial-resolution radar imagery (e.g., TerraSAR-X). This article presents a baseline linear combination (BLC) approach to generate interferograms with nearly zero baselines so as to minimize the effects of the uncertainties in the DEM used. It incorporates the baseline combination (BC) method with adjacent gradient networking to successfully unwrap the interferograms even in abruptly discontinuous areas, which in turn can be used to estimate a high-resolution DEM. The BLC approach does not require any deformation model; instead, it utilizes nearly zero-baseline interferograms to assist with 3-D phase unwrapping. Application of the BLC approach to the TerraSAR-X data set in Shenzhen, China, shows that the BLC-derived DEM agrees with the digital surface model (DSM) obtained from light detection and ranging (LiDAR) with a correlation coefficient of 0.998 and a root-mean-square error (RMSE) of 2.05 m, demonstrating the effectiveness of the BLC approach. Note that the BLC approach is not only able to be employed in urban areas with high buildings but also in mountain areas with steep slopes.