Identification of the mangrove species using UAV hyperspectral images: A case study of Zhangjiangkou mangrove national nature reserve
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摘要: 红树林种群的组成和分布对于红树林生态系统的保护和恢复至关重要。本研究以漳江口红树林保护区为研究对象,通过获取无人机高光谱影像,进行光谱特征分析、光谱微分变换和包络线去除,提取了911组17个光谱特征参数,通过逐步判别分析筛选出13个用于决策树构建的特征参数,最终通过C5.0决策树模型获得了研究区红树林种群的分布状况。结果表明,漳江口红树林保护区植被种群呈现自上到下不同类型的分布情况,研究区上部以桐花树和秋茄混合类型为主,中间区域呈现白骨壤、桐花树和秋茄三者共生的现状,研究区下部则以白骨壤分布为主,伴生有少量的秋茄。通过混淆矩阵计算,得到研究区总体分类精度为 87.95%,Kappa系数为 83.81%,具有较好的精度。研究结果可为区域红树林湿地保护提供数据支撑,为红树林种群识别研究提供方法参考。Abstract: The composition and distribution of mangrove species are crucial to the protection and restoration of mangrove wetland ecosystems. In this study, mangrove species distribution was identified by unmanned aerial vehicle (UAV) hyperspectral images from Zhangjiangkou mangrove national nature reserve. Spectral characteristics, spectral differential, and spectral continuum removal were analyzed, 17 spectral parameters of 911 group spectral data from different vegetation species were obtained. Furthermore, 13 parameters for decision tree construction were selected by stepwise discriminant analysis. As a result, an accurate distribution map of mangrove species in the study area was obtained through C5.0 decision tree classification model. The vegetation species present different distribution types from top to bottom in the Zhangjiangkou mangrove national nature reserve. The upper part of the study area was dominated by the mixed type of Aegiceras corniculatum and Kandelia obovata. The middle area showed symbiosis status of three different mangrove species Avicennia marina, Aegiceras corniculatum and Kandelia obovata. The lower part of the study area was dominated by Avicennia marina, and a small amount of Kandelia obovata. Through the confusion matrix, the overall classification accuracy is 87.95% and the Kappa coefficient is 83.81%, showed a satisfactory precision. Therefore, our mangrove species identification results from UAV hyperspectral images could be used as a reference for ecological protection of regional mangrove wetland, and also as a identification method reference for mangrove species.
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Key words:
- mangrove /
- Zhangjiangkou /
- unmanned aerial vehicle (UAV) /
- hyperspectral images /
- species identification
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表 1 研究区典型植被类型样本情况表
Tab. 1 The information sheet of sample of the typical vegetation species in the study area
植被类型 桐花树 白骨壤 秋茄 互花米草 训练样本数 458 188 102 163 验证样本数 121 94 83 95 表 2 研究区典型植被类型“三边”参数
Tab. 2 Three sides spectral parameters of the typical vegetation species in the study area
植被类型 Db Dy Dr Sb Sy Sr 桐花树 0.002 −0.014 0.726 −0.239 −0.189 8.892 白骨壤 0.006 −0.031 0.791 −0.398 −0.312 10.313 秋茄 0.009 −0.035 0.827 −0.458 −0.307 10.292 互花米草 0.026 −0.001 0.245 −0.076 −0.098 3.047 表 3 研究区典型植被类型最大峰度统计
Tab. 3 The maximum kurtosis of the typical vegetation species in the study area
植被类型 650~700 nm 700~720 nm 720~750 nm K1 B1 K2 B2 K3 B3 桐花树 0.019 9 690 0.024 8 718 0.031 6 738 白骨壤 0.027 8 690 0.019 4 714 0.029 6 738 秋茄 0.029 1 690 0.023 1 714 0.032 4 730 互花米草 0.009 3 690 0.009 3 718 0.015 4 742 注:K1、K2、K3分别为各波段范围内的最大峰度值;B1、B2、B3分别为各峰度对应的波段值。 表 4 研究区典型植被类型包络线去除光谱吸收参数
Tab. 4 Spectral absorption parameters after continuum removal of typical species in the study area
植被类型 H1 H2 AL1 AL2 A1 A2 S1 S2 桐花树 0.446 7 0.916 0 15.061 0 86.550 7 24.359 9 127.111 5 0.618 3 0.680 9 白骨壤 0.420 4 0.849 3 13.791 8 76.755 4 24.419 1 112.484 6 0.564 8 0.682 4 秋茄 0.507 4 0.893 8 15.476 2 84.054 6 30.705 8 119.929 1 0.504 0 0.700 9 互花米草 0.114 7 0.479 6 2.587 4 36.971 9 6.328 5 56.787 7 0.408 9 0.651 1 注:H1、AL1、A1、S1为450~550 nm波段范围内的参数值;H2、AL2、A2、S2为550~750 nm波段范围内的参数值。 表 5 研究区典型植被分类结果混淆矩阵
Tab. 5 Confusion matrix of classification results of the typical vegetation species in the study area
桐花树 白骨壤 秋茄 互花米草 总计 用户精度/% 桐花树 131 3 12 0 146 89.72 白骨壤 3 108 4 6 121 89.25 秋茄 12 4 113 3 132 85.60 互花米草 2 7 4 86 99 86.86 总计 148 122 133 95 498 − 生产精度/% 88.51 88.52 84.96 90.52 − − 注:−代表空值。 -
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