Mathematical Model Guided Interpolation for Mapping SRTM Understory Terrain by Integrating ICESat-2 Data

To enhance the accuracy of the Shuttle Radar Topography Mission (SRTM) DEM, this study establishes a mathematical modeling approach based on Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) data to interpolate and correct the SRTM DEM of understory terrain. Puerto Rico in the United States was selected as the study area. First, the elevation error was obtained by matching ICESat-2 with SRTM DEM. Then, interpolation models for SRTM DEM were built using the methods of IDW, Kriging, Spatial Analyst, and Trend for correction. Finally, the accuracy of the interpolate models was evaluated based on ICESat-2 data. In addition, to explore the factors influencing the elevation accuracy of SRTM DEM, linear regression analysis was conducted on two dimensions: canopy height and forest type. The results indicate that this method significantly improves the accuracy of the SRTM DEM in understory terrain, and the IDW interpolation model proved to be the most effective, reducing RMSE from 13.40 to 6.74 m, improving the elevation accuracy of SRTM DEM for understory terrain by 49%. This achievement not only provides an effective method for improving the quality of SRTM DEM but also lays a solid foundation for subsequent geospatial analysis and environmental monitoring work.