Evaluation of the performance of GaoFen-7 laser altimeter data for ground elevation retrieval over vegetated areas

The Gao Fen-7 (GF-7) satellite employs a laser altimeter to provide the global measurement of ground elevation. This study aimed to evaluate the performance of GF-7 laser altimeter data in ground elevation retrieval over vegetated areas. First, GF-7 waveforms were processed to obtain the ground elevation. Second, we verified the ground elevation accuracy using airborne light detection and ranging (LiDAR) data. Finally, we analysed the influence of various factors (e.g., slope, signal-to-noise ratio (SNR), vegetation height) on ground elevation estimation. Results showed that the lowest Gaussian peak best represents the ground elevation, with root mean squared error (RMSE) and mean error of 2.30 m and 0.28 m, respectively. The laser 1 performs better than laser 2 in ground elevation retrieval as indicated by the lower RMSE. The ground elevation accuracy differed significantly across various land cover types and showed a pattern of lower estimation accuracy with more complex vertical structure. Additionally, results also indicated that the ground elevation accuracy decreased with increasing slope, vegetation height and vegetation coverage but increased with increasing SNR. Overall, our study found that GF-7 laser altimeter data have a strong capability to retrieve the ground elevation over vegetated areas.