JOURNAL OF NANJING FORESTRY UNIVERSITY ›› 2023, Vol. 47 ›› Issue (5): 9-18.doi: 10.12302/j.issn.1000-2006.202209011

Special Issue: 林草计算机应用研究专题

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Crown segmentation of CHM based on the enhanced frost local filtering and distance map reconstruction

ZHANG Huacong1,2,3(), TAN Xinjian3(), YU Longhua3, LI Yueqiao3, CHEN Yongfu1,2, LIU Ren3, ZHANG Huaiqing1,2,*()   

  1. 1. Institute of Forest Resource Information Techniques, CAF, Beijing 100091, China
    2. Key Laboratory of Remote Sensing and Information, NFGA, Beijing 100091, China
    3. Experimental Enter of Subtropical Forestry, CAF, Xinyu 336600, China
  • Received:2022-09-05 Revised:2022-10-25 Online:2023-09-30 Published:2023-10-10

Abstract:

【Objective】We used the enhanced Frost local filtering and single-tree distance map reconstruction marking technology to segment a canopy height model (CHM), improving the accuracy and efficiency of unpiloted aerial system (UAV)-light detection and ranging (LiDAR) segmentation in single-tree crowns.【Method】 We selected three forest types - coniferous mixed, coniferous-broad mixed, and broad-leaved mixed - in the Shanxia Experimental Forest Farm of Fenyi, Jiangxi Province. We then used UAV-LiDAR data to construct the CHM. To combat the increased pores in the crown area of the high-resolution CHM, we used the enhanced Frost local filtering to optimize the CHM and results were compared with different filtering methods. Next we applied the distance map reconstruction marker segmentation technology to segment and analyze the CHM-with resolutions of 0.1, 0.2, 0.5 and 1.0 m after optimization of the enhanced Froest local filter. Finally, we determined the CHM with the optimal resolution, and compared segmentation results with that of a watershed algorithm with the same resolution and mean-shift segmentation algorithm. 【Result】 Applying the enhanced Frost local filter indeed optimized the CHM-preserving image details while suppressing phase crown noise. A resolution of 0.2 m performed best for the CHM segmentation. An overall accuracy of 0.96, 0.84 and 0.75 was observed for coniferous mixed, coniferous-broad mixed, and broad-leaved mixed forests, respectively. The crown width of a single tree was calculated according to crown segmentation results, and the R2 estimated at 0.83, 0.82 and 0.71, respectively. 【Conclusion】Through the enhanced Frost local filtering and distance map reconstruction marking technology, the single-tree segmentation and crown estimation of laser point cloud CHMs can be realized, meeting key requirements of forest surveys and monitoring.

Key words: UAV laser point cloud, cannopy height model(CHM), enhance Frost, distance map marker and reconstruction, crown segmentation

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