Journal of Geo-information Science >
Study of Factors Impacting the Tree Height Extraction Based on Airborne LIDAR Data
Received date: 2014-02-20
Request revised date: 2014-03-20
Online published: 2014-11-01
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The purpose of this study is to evaluate the accuracy of extracting average height of natural secondary forest using airborne LIDAR data and to explore the problems that accompany. The DSMs and DEMs with differentspatial resolutions were simulated, by applying HASM-AD algorithm. DSM minus DEM gives CHM, and the tree heights were extracted from CHM. We applied tree vertex recognition algorithm with different recognition scopes. Using 30 measured plot data for verification, we tried to express how CHM spatial revolutionand recognition scope could affect tree height extraction accuracy. Firstly, we produced the 0.5 m resolution of CHM and gave 3 trials with setting the recognition scope radius as 0.5 m, 1.0 m and 1.5 m consecutively. The contrast between the results showed that the number of tree vertices extracted was the largest when the recognition scope radius was set as 0.5 m. The algorithm's ability to recognize tree vertex decreases as recognition scope radius increases. Then, we set the recognition scope radius as 0.5 m unchanged and gave 3 trials in which we extracted tree vertex from different CHM with 3 different resolutions (0.1 m, 0.25 m, 0.5 m). The results showed that the number of tree vertices extracted in 3 trials were close. In other words, the recognition scope radius could hardly influence tree vertex extraction. Finally, we compared the average value of the extracted tree heights in each plot to the average of the measured values. The result showed that they were highly correlated with each other, and the regression coefficient between them was 0.694. In conclusion, the recognition scope radius has great influence on tree vertex extraction, while resolution of CHM has little influence on tree vertex extraction. Increasing the sampling density of LIDAR data, choosing an appropriate CHM simulation method and improving the tree vertex recognition algorithm can increase the accuracy of tree height extraction.
Key words: airborne LIDAR; HASM; tree height; Tianlaochi; natural secondary forest
WANG Yifu , YUE Tianxiang , ZHAO Mingwei , DU Zhengping , LIU Xiangfeng , LIU Shuang , SONG Erfei , SUN Wenzheng , ZHANG Yanli . Study of Factors Impacting the Tree Height Extraction Based on Airborne LIDAR Data[J]. Journal of Geo-information Science, 2014 , 16(6) : 958 -964 . DOI: 10.3724/SP.J.1047.2014.00958
Tab. 1 Description of plots表1 样地基本信息表 |
样地号 | 森林类型 | 株数 | 平均树高(m) | 最大树高(m) | 最小树高(m) | 平均胸径(cm) | 样地号 | 森林类型 | 株数 | 平均树高(m) | 最大树高(m) | 最小树高(m) | 平均胸径(cm) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | 祁连圆柏 | 30 | 7.3 | 11.3 | 2.2 | 29.7 | 16 | 青海云杉 | 34 | 11.0 | 21.2 | 2.6 | 15.6 |
2 | 祁连圆柏 | 13 | 8.8 | 12.7 | 2.5 | 33.5 | 17 | 青海云杉 | 27 | 13.0 | 21.6 | 2.4 | 19.8 |
3 | 青海云杉 | 60 | 3.4 | 19.3 | 0.5 | 9.9 | 18 | 青海云杉 | 40 | 12.8 | 26.3 | 2.0 | 16.1 |
4 | 青海云杉 | 17 | 11.1 | 18.6 | 0.8 | 21.7 | 19 | 青海云杉 | 39 | 10.4 | 21.6 | 2.3 | 15.0 |
5 | 混交林 | 36 | 4.0 | 10.7 | 1.3 | 8.2 | 20 | 青海云杉 | 46 | 10.7 | 20.8 | 2.9 | 13.7 |
6 | 青海云杉 | 106 | 7.1 | 16.9 | 1.8 | 9.9 | 21 | 青海云杉 | 108 | 9.0 | 13.6 | 4.4 | 10.0 |
7 | 青海云杉 | 21 | 9.9 | 20.4 | 1.7 | 20.1 | 22 | 青海云杉 | 20 | 13.5 | 22.8 | 3.5 | 18.8 |
8 | 青海云杉 | 65 | 8.0 | 17.7 | 2.0 | 13.2 | 23 | 青海云杉 | 25 | 10.8 | 20.0 | 4.5 | 15.6 |
9 | 青海云杉 | 44 | 7.7 | 17.0 | 2.2 | 12.6 | 24 | 青海云杉 | 37 | 7.7 | 17.3 | 2.6 | 10.4 |
10 | 青海云杉 | 22 | 7.1 | 20.1 | 1.5 | 13.8 | 25 | 青海云杉 | 26 | 11.4 | 21.8 | 3.2 | 17.6 |
11 | 青海云杉 | 16 | 10.7 | 25.0 | 2.5 | 21.3 | 26 | 青海云杉 | 26 | 12.4 | 22.1 | 3.9 | 16.9 |
12 | 青海云杉 | 16 | 11.7 | 25.3 | 1.8 | 25.3 | 27 | 青海云杉 | 34 | 10.4 | 22.4 | 3.5 | 14.6 |
13 | 青海云杉 | 6 | 21.1 | 24.4 | 15.1 | 39.1 | 28 | 青海云杉 | 11 | 20.3 | 31.1 | 4.8 | 30.2 |
14 | 青海云杉 | 49 | 9.4 | 19.9 | 2.0 | 14.2 | 29 | 青海云杉 | 29 | 14.6 | 26.6 | 4.6 | 20.4 |
15 | 青海云杉 | 17 | 14.0 | 21.8 | 3.0 | 23.5 | 30 | 混交林 | 19 | 10.2 | 23.4 | 2.8 | 22.5 |
Fig. 1 Distribution of plots图1 样地分布图 |
Fig. 2 Compution units of HASM-AD algorithm图2 HASM-AD算法计算窗口 |
Fig. 3 Flow chart图3 单木树高提取算法流程图 |
Tab. 2 Parameter settings of comparison trials表2 对比试验参数设置 |
实验 | 分辨率(m) | 搜索半径(m) |
---|---|---|
1 | 0.1×0.1 | 0.5 |
2 | 0.25×0.25 | 0.5 |
3 | 0.5×0.5 | 0.5 |
4 | 0.5×0.5 | 1.0 |
5 | 0.5×0.5 | 1.5 |
Fig. 4 The influence of the parameter setting on tree vertex extracting图4 参数设置对树顶点提取的影响 |
Fig. 5 Tree height extraction results in Tianlaochi图5 天涝池树高识别提取结果 |
Fig. 6 Regression analysis between extracted tree height/number and measured tree height/number图6 提取树高和株数与实测值的回归分析 |
Tab. 3 Linear dependence between extracted tree height and measured tree height表3 提取树高与实测树高的线性回归关系 |
线性回归方程 | R2 | 说明 |
---|---|---|
y1=0.819x1+5.032 | 0.694 | y1、x1分别为提取的样地平均树高和实测值 |
y2=0.845x2+2.390 | 0.850 | y2、x2分别为提取的样地最大树高和实测值 |
y3=1.582x3+2.340 | 0.111 | y3、x3分别为提取的样地最小树高和实测值 |
y4=0.145x4+10.01 | 0.339 | y4、x4分别为提取的样地株数和实测值 |
Fig. 7 Simulation of CHM’s generating图7 CHM生成示意图 |
The authors have declared that no competing interests exist.
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