Table 1_Accuracy assessment of topography and forest canopy height in complex terrain conditions of Southern China using ICESat-2 and GEDI data.docx

ICESat-2 and GEDI offer unique capabilities for terrain and canopy height retrievals; however, their performance and measurement precision are significantly affected by terrain conditions. Furthermore, differences in data scales complicate direct comparisons of their measurement capabilities. This study evaluates the accuracy of terrain and canopy height retrievals from ICESat-2 and GEDI LiDAR data in complex terrain environments. Jinghong City and Pu’er City in Southwest China were selected as study areas, with high-precision airborne LiDAR data serving as a reference. Ground elevation and canopy height retrieval accuracies were compared before and after scale unification to 30 m × 30 m under varying slope conditions. Results indicate that ICESat-2 shows a significant advantage in terrain height retrieval, with RMSE values of 4.75 m and 4.21 m before and after scale unification, respectively. In comparison, GEDI achieved RMSE values of 4.94 m and 4.96 m. Both systems maintain high accuracy in flat regions, but accuracy declines with increasing slope. For canopy height retrieval, GEDI outperforms ICESat-2. Before scale unification, GEDI achieved an R² of 0.73 with an RMSE of 5.15 m, and after scale unification, an R² of 0.67 with an RMSE of 5.32 m. In contrast, ICESat-2 showed lower performance, with an R² of 0.65 and RMSE of 7.42 m before unification, and an R² of 0.53 with RMSE of 8.29 m after unification. GEDI maintains higher canopy height accuracy across all slope levels. Post-scale unification, both systems show high accuracy in ground elevation retrieval, with ICESat-2 being superior. In contrast, GEDI achieves better canopy height retrieval accuracy. These findings highlight the synergistic strengths of ICESat-2’s photon-counting and GEDI’s full-waveform LiDAR techniques, demonstrating advancements in satellite laser altimetry for terrain and canopy height retrieval.

ICESat-2与GEDI在地形与冠层高度反演领域具备独特优势，但其性能与测量精度显著受地形条件影响。此外，数据尺度的差异使得直接对比二者的测量能力变得更为复杂。本研究选取中国西南部的景洪市与普洱市作为研究区域，以高精度机载激光雷达（LiDAR）数据作为参考基准，评估了ICESat-2与GEDI激光雷达数据在复杂地形环境下的地形与冠层高度反演精度。在不同坡度条件下，分别对比了将数据统一至30 m×30 m尺度前后，二者的地面高程与冠层高度反演精度。结果表明，ICESat-2在地形高度反演方面具备显著优势，尺度统一前后的均方根误差（Root Mean Square Error, RMSE）分别为4.75 m与4.21 m；相较之下，GEDI的均方根误差则为4.94 m与4.96 m。两种系统在平坦区域均能保持较高反演精度，但随着坡度升高，反演精度均出现下降。针对冠层高度反演，GEDI的表现优于ICESat-2：尺度统一前，GEDI的决定系数（Coefficient of Determination, R²）为0.73，均方根误差为5.15 m；尺度统一后，其决定系数为0.67，均方根误差为5.32 m。与之相对，ICESat-2的反演性能更低，尺度统一前的决定系数为0.65、均方根误差为7.42 m，尺度统一后则为决定系数0.53、均方根误差8.29 m。GEDI在所有坡度等级下均能保持更高的冠层高度反演精度。尺度统一后，两种系统在地面高程反演方面均具备较高精度，且ICESat-2表现更优；而在冠层高度反演中，GEDI则能取得更优精度。上述研究结果凸显了ICESat-2的光子计数激光雷达技术与GEDI的全波形激光雷达技术的协同优势，证明了卫星激光测高在地形与冠层高度反演领域的技术进展。