星载多站层析SAR森林高度反演初探

Synthetic Aperture Radar Tomography (TomoSAR), by virtue of its three-dimensional (3D) resolution capability, can be used to study the 3D structure of semitransparent targets, such as forests, icebergs, and snowpacks. Currently, TomoSAR measurements, especially spaceborne TomoSAR, are mostly obtained through repeat-pass observations, which introduce two major problems: Temporal decorrelation and signal delay caused by the troposphere or ionosphere. Severe temporal decorrelation and signal delay can lead to defocused tomograms, which make it impossible to reconstruct the 3D structure of a target. Unlike repeat-pass TomoSAR systems, multi-static TomoSAR systems simultaneously collect multibaseline images, reducing temporal decorrelation to zero and canceling all types of signal delay, making them an ideal tool for 3D TomoSAR reconstruction. The Hongtu-1 constellation, launched in 2023 and operated by PIESAT Information Technology Limited, is the world’s first spaceborne multi-static SAR system. In this paper, we conduct spaceborne multi-static TomoSAR processing and forest height estimation experiments using Hongtu-1 multi-static images. By comparing tomograms from tropical and temperate forests, it is found that the X-band signal from Hongtu-1 cannot reach the ground in dense tropical forests, but can in temperate forests, due to much lower tree and leaf density. This indicates that Hongtu-1 is capable of forest height measurement in temperate forests. By comparing forest height inversion in temperate forests obtained from Hongtu-1 TomoSAR and GEDI LiDAR, it is found that, at the test sites considered in this paper, Hongtu-1 TomoSAR measurements can provide more accurate forest height inversion (with a 35% improvement), more measurement points, and higher-resolution products than GEDI, which further demonstrates the capability and superiority of Hongtu-1 TomoSAR in forest height estimation.