A Spatial Alignment Method for UAV LiDAR Strip Adjustment in Nonurban Scenes

LiDAR strip adjustment is a key prerequisite for subsequent applications based on point cloud data since it inevitably suffers from spatial discrepancies caused by laser ranging errors, mounting errors, etc. Most current LiDAR strip adjustment methods rely on the extraction of structural features which are often unsuitable for non-urban scenes. Alternative strip adjustment methods based on correspondence distance minimalization ignore spatial alignment. To overcome these limitations, this paper presents an accurate spatial alignment method for UAV LiDAR strip adjustment in non-urban scenes. Firstly, we construct a novel point cloud feature descriptor called Spherical Shell Point Feature (SSPF) to extract multi-dimensional non-structural features that are robust to non-urban point clouds. The constructed SSPF is then combined with point coordinates to generate embedded features, which simultaneously consider the point coordinates and spatial alignment. Finally, the embedded features are utilized by a two-stage matching method to match pair-wise points of two adjacent strips. The proposed method is validated on two non-urban datasets collected by two types of LiDARs, which reduces the digital surface model discrepancies by 0.252 m and 0.221 m , respectively, and proves its superiority compared to mainstream strip adjustment methods as well.