Topography Retrieval From Single-Pass POLSAR Data Based on the Polarization-Dependent Intensity Ratio

Abstract

At present, many polarimetric synthetic aperture radar (POLSAR) remote sensing applications still perform radio metric terrain correction, whereas other types of terrain slope analysis rely on Shuttle Radar Topography Mission and Advanced Spaceborne Thermal Emission and Reflection Radiometer digital elevation model (DEM) databases. However, the terrain relief characteristics present in fully POLSAR images can also be used for topography retrieval from single-flight data. Based on the analysis of the polarization signature peak shift, we propose a new topography retrieval algorithm based on the polarization-dependent intensity ratio. The intensity term conforms to both the polarimetric orientation angle shift model and the Lambertian scattering model, which is refined for synthetic aperture radar (SAR) imaging geometry. This is useful in avoiding solving an ill-conditioned problem, and it is more practical than considering the two models independently. Another key idea of this algorithm is the derivation of a second-order residual error equation for revising the ground-range slope error with homogeneous media using the full multigrid (FMG) technique. Furthermore, the “fake” topographic relief effect induced by geophysical terrain variations is also considered and reduced by including an $\bar{\alpha} $ scattering angle-based weighting coefficient in the second-order residual error equation. In addition, a first-order residual error equation combined with tie points is proposed for calculating the least squares estimation of the height from slope integration by FMG. National Aeronautics and Space Administration Jet Propulsion Laboratory AIRSAR and UAVSAR L-band POLSAR and interferometry SAR DEM data are used to illustrate and validate this algorithm. Our results demonstrate the high potential of this method for employing a low- resolution DEM to match the corresponding high-resolution POLSAR data.