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Scientia Silvae Sinicae ›› 2022, Vol. 58 ›› Issue (10): 111-120.doi: 10.11707/j.1001-7488.20221011

• Special Issue: Forest Fire Prevention Relevant Resource Monitoring, Analysis and Management Techniques in Zhangjiakou Competition Area of the Beijing Olympic Winter Games • Previous Articles     Next Articles

Extraction of Healthy Canopy of New Afforestation for Pinus tabulaeformis Based on UAV High-Resolution Image

Xuzhan Guo1,2,3,Qiao Chen1,3,Xiaofang Zhang1,3,Liang Hong1,3,4,Yuanyuan You5,Shouzheng Tang1,3,Liyong Fu1,3,*   

  1. 1. Research Institule of Forest Resource Information Techniques, CAF Beijing 100091
    2. College of Computer and Information Technology, Xinyang Normal University Xinyang 464000
    3. Key Laboratory of Forest Management and Growth Modeling, National Forestry and Grassland Administration Beijing 100091
    4. College of Mathematics and Statistics, Xinyang Normal University Xinyang 464000
    5. Forestry and Grassland Bureau of Chongli District, Zhangjiakou City, Hebei Province Zhangjiakou 075000
  • Received:2021-12-22 Online:2022-10-25 Published:2023-04-23
  • Contact: Liyong Fu

Abstract:

Objective: Based on the spectral characteristics and spacial interlacing of healthy tree crowns in new afforestation, the spectral enhancement method and multi-scale segmentation thresholds of healthy tree crowns under complex ground vegetation conditions were discussed to provide technical support for the daily monitoring of afforestation verification. Method: The UAV images of newly planted trees in the core area of the Winter Olympics were chosen as experimental data. Firstly, based on the different color characteristics of healthy tree crowns and other disturbances, the images were enhanced by homomorphic filtering and transformed by ExG spectral index. Then, the Otsu method was used to obtain the binary image, and the multi-scale morphological filtering method was used for segmentation and fusion to segment the interlaced crown areas, correspondingly extract the possible healthy crown areas in the original image. Finally, based on the feature vector constructed by the color vector, the GLCM and the LBP, the random forest was used to classify the extracted area to detect the healthy tree crowns in the image. Result: The method based on spectral index transformation and multi-scale morphological filtering was able to effectively segment the interlaced and continuous crown areas, exclude other interference objects those were similar in color to healthy trees and accurately extract the areas those might be crowns. The 17 UAV orthophoto images with varying stand densities and lighting conditions were tested, and the crown centers were marked by visual interpretation. Furthermore, the three evaluation indexes: precision, recall and F1 score were used to quantitatively compare and analyze the recognition effects of random forest and SVM. The experimental result showed that 96.78% of the crowns were extracted using the multi-scale morphological filtering method, and the F1 score of random forest was higher than 97%, while the recall of support vector machine was significantly lower than that of random forest. Conclusion: Our result showed that the crown extraction method based on spectral index transformation and multi-scale morphological filtering could be able to extract the healthy crown quickly and accurately in the UAV images and effectively complete the afforestation verification.

Key words: UAV image, homomorphic filtering, spectral index, morphological filtering, random forest

CLC Number: