A Pre-Pruning Quadtree Isolation Method with Changing Threshold for ICESat-2 Bathymetric Photon Extraction

The new generation of spaceborne laser altimeter, the Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2), which can simultaneously generate reflections on water surface underwater, is a potential data source for exploring depth in nearshore environments. To achieve this scientific goal, accurate bathymetric photon extraction needed. This study proposed pre-pruning quadtree isolation (PQI) method with changing threshold. Firstly, step introduced. Photons are transformed into different levels isolated structure according to spatial density. Then, frequency histogram elevation level (IL) generated, IL thresholds ranges calculated by Otsu method, photons extracted. results Culebra archive show that achieved 92.71% F1 score. Noise rate main factors affecting sounding photons. When density gradually increases from 2–4 pts/m 6–8 pts/m, score PQI decreases no more than two percent. In ranges, also better those comparison methods. Therefore, provide reliable theoretical support areas lacking data.