Combined Adjustment for Very High-Resolution Satellite Stereo Images and ICESat-2 Laser Altimetry Data

As we all know, the combined block adjustment of very high-resolution satellite stereo images (VHRSIs) and spaceborne laser altimetry data (Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) data) can provide support for 1:10000 topographic mapping without the use of ground control points (GCPs). However, there are still many challenges in the combined adjustment processing, such as the selection of elevation control points and the registration of two types of data. To address these issues in combined adjustment, a preliminary method for selecting elevation control points is proposed based on various laser attribute information, building utilizing an analysis of ATL08 product characteristics. Furthermore, virtual planar control points and elevation checkpoints are introduced, and a combined block adjustment strategy is designed to refine the application of laser elevation control points and resolve registration issues between the stereo image data and laser altimetry data during the adjustment process. The proposed strategy was implemented and evaluated across three representative experimental areas. In the experiments, the elevation root-mean-square errors (RMSEs) of processed stereo images in all three areas were found to be below 1 m, while the planimetric accuracy remained consistent with the results obtained from the free network adjustment. The findings suggest that the developed strategy effectively addresses the challenges associated with elevation control point selection and data registration in the combined adjustment process, significantly enhancing elevation accuracy while preserving the planar accuracy of stereo images. Therefore, the proposed combined block adjustment strategy supports the endeavor of global 1:10000 mapping without the need for GCPs and promotes the application of VHRSI and ICESat-2 data in land surface surveying and mapping.