Fig. 1. Point cloud coarse denoising results

Fig. 2. Point cloud fine removal noise process

Fig. 3. Schematic diagram of slope angle calculation of point cloud data and data segmentation processing diagram，(a) the angle of the elliptical domain under different slope angles, (b) slope angle calculation, (c) data segmentation, (d) consolidation of data segments

Fig. 4. The density cluster threshold is determined

Fig. 5. Specific clustering removal noise process

Fig. 6. Point cloud data fine removal noise

Fig. 7. ICESat-2 satellite transit area in the Area of Yellowstone National Park and Great Smoky Mountains Forest Park in the United States

Fig. 8. The spaceborne photon counting lidar matches the NEON data

Fig. 9. ATLAS data matches onboard data

Fig. 10. Denoising results of different denoising algorithms: (a) (d) (g) (j) the result of the algorithm of this paper processing Data1-4, (b) (e) (h) (k) the result of the LOF algorithm processing Data1-4, (c) (f) (i) (l) the result of the DBSCAN algorithm processing Data1-4

Fig. 11. Comparison of ground curves for different data

Fig. 12. Comparison of crown curves in different data

Fig. 13. The algorithm in this paper is compared with ATL08 data，(a)、(c)、(e)、(g) the results of processing and classifying Data1-4 for the algorithm herein, (b)、(d)、(f)、(h) the ATL08 data corresponding to Data1-4