Extraction Strategy for ICESat-2 Elevation Control Points Based on ATL08 Product

ICESat-2 can obtain high-precision 3-D measurement information of targets and has a unique advantage in determining global elevation control points. However, due to the influence of the atmospheric environment, target characteristics, hardware equipment, and other factors, its elevation accuracy is not highly reliable, and not all data points can be used as control points. To obtain high-precision elevation control points from ICESat-2 data products, an extraction strategy that combines the accuracy and location requirements for control points was developed based on the ATL08 product. Multiple attribute parameters were incorporated into the extraction procedure, including terrain factor information, segment elevation information, cloud confidence flag, surface coverage data, topographic photon quantity, and photon height difference information. The extraction approach was then performed and analyzed using experimental data from the Hanzhong area in Shanxi province and the Songshan area in Henan province. In the experiments, the root-mean-square error (RMSE) of the extracted data points in two areas was both about 0.5 m and could reach 0.3 m after eliminating gross error points caused by surface changes and misclassification. The results suggest that the developed strategy takes into account the point location requirements of control points, can overcome the influence of complex terrain and ground objects, and significantly improve the overall accuracy of obtained control points. Therefore, the proposed extraction strategy can support the establishment of the global elevation control point database and promote the application of ICESat-2 data in land surface surveying and mapping.