ACCURACY EVALUATION OF ICESAT-2 ATL08 IN FINLAND

Abstract. ATL08 is level-3A land and vegetation height product of ICESat-2 data, which recorded the terrain elevation and surface height parameters at 100 m fixed-length along the ground track. It has been used widely not only in vegetation monitoring at large scale, but also in improving the accuracy of satellite stereo mapping, so, the accuracy of ATL08 product is the precondition of its application. Although some studies have evaluated the terrain and canopy height retrieval accuracy of ATL08, it is still not comprehensive that most studies focus on the accuracy in vegetation area. In this study, the performance on terrain and surface height retrieval of ATL08 was evaluated both in forested and non-forested area based on DEM and ALS data in Finland. A total of 6,682,846 and 3,980,235 segments were used to evaluate the accuracy of terrain and surface height retrieval, respectively. The result showed that, firstly, terrain elevation retrieval from ICESat-2/ATLAS is accurate, e.g., sub-meter level both in forested and non-forested area and slope was an important factor affecting the accuracy of terrain retrieval, while, surface height retrieval was low accurate, e.g., the RMSE of surface height retrieval were more than 5 m. Secondly, the accuracy of terrain elevation retrieval in non-forested area was slightly higher than that in forested area showed by MAE and RMSE. Finally, the accuracy of surface height retrieval in forested area was higher than that in non-forested area, and it should be emphasized that there is a significantly difference on RMSE% between forested and non-forested area. The study indicated that the terrain elevation retrieval from ATL08 is relative reliable and recommended to use when the accuracy is not strictly required, while, the use of surface height should be considered carefully and avoid to use low accuracy observation.