Extraction of deciduous coniferous forest based on Google earth engine (GEE) and Sentinel-2 image
-
摘要:
目的 针对森林资源精细监测评价的需求,探索多时相、多特征的Sentinel-2影像在落叶针叶林识别中的应用潜力,根据落叶针叶林的物候特征构建分类模型,为大范围落叶针叶林识别提供方法参考。 方法 基于GEE平台,以黑龙江省孟家岗林场为研究区,分析不同季节落叶针叶林与其他森林之间的差异。研究使用2020年春季(5月7日和5月27日)、夏季(8月9日)和秋季(10月19日)的4景Sentinel-2影像,提取光谱特征、纹理特征和地形特征构建多特征数据集,根据特征重要性得分进行特征优选,最后使用随机森林分类器得到落叶针叶林识别的最佳模型,实现孟家岗林场落叶针叶林的精确提取。 结果 试验结果表明落叶针叶林具有明显的植被光谱特征和季相特性,多时相影像数据包含落叶针叶林更多物候期,春季和秋季的影像更有利于区分落叶针叶林与其他森林。此外,近红外、短波红外波段的光谱信息对识别落叶针叶林有较大帮助。利用 GEE平台和多时相Sentinel-2影像可以高效快速地提取植被信息,落叶针叶林提取总体精度与Kappa系数分别达到 91.20%,0.82。 结论 基于GEE平台和Sentinel-2影像构建的分类模型对落叶针叶林信息的快速提取有一定的可行性和适用性,研究结果对大面积落叶针叶林的空间位置分布提取具有一定的参考价值。 -
关键词:
- 落叶针叶林 /
- Sentinel-2影像 /
- 物候特征 /
- 随机森林 /
- GEE平台
Abstract:Objective In view of fine monitoring and evaluation needs of forest resources, the application potential of multi-temporal and multi-feature Sentinel-2 images in the identification of deciduous coniferous forests was exploratively studied, and a classification model was built according to the phenological characteristics of deciduous coniferous forests to provide method reference for identifying deciduous coniferous forests on a large scale. Method Based on the GEE platform, the difference between deciduous coniferous forests and other forests in different seasons was analyzed by taking Mengjiagang Forest Farm in Heilongjiang Province of northeastern China as the research area. In this study, four seasonal Sentinel-2 images of spring (May 7 and May 27), summer (August 9), and autumn (October 19) in 2020 were used to construct a multi-feature dataset by extracting spectral features, texture features, and topographic features. Feature optimization was carried out according to feature importance scores. Finally, the optimal model for identifying deciduous coniferous forests was established by a random forest classifier to achieve rapid extraction of deciduous coniferous forest in Mengjiagang Forest Farm. Result The experimental results showed that deciduous coniferous forests displayed obvious vegetation spectral features and seasonal characteristics. The multi-temporal image data contained more phenological period information on deciduous coniferous forests, and the images in spring and autumn can enable better differentiation between deciduous coniferous forests and other forests. In addition, near-infrared and short-wave infrared spectral information can greatly help identify deciduous coniferous forests. By the GEE platform and multi-temporal Sentinel-2 images, it is possible to extract vegetation information efficiently and quickly. The overall extraction accuracy and Kappa coefficient of deciduous coniferous forest reached 91.20% and 0.82, respectively. Conclusion The classification model constructed based on the GEE platform and Sentinel-2 image has certain feasibility and applicability for the rapid extraction of deciduous coniferous forest information, and the research results provide a certain reference value for the large-scale extraction of spatial location distribution information of deciduous coniferous forest. -
表 1 Sentinel-2光谱波段信息
Table 1. Sentinel-2 spectral band information
波段
Band描述
Description中心波长
Central
wavelength/nm分辨率
Resolution/mB2 蓝光 Blue light 497 10 B3 绿光 Green light 560 10 B4 红光 Red light 665 10 B5 红边1 Red edge 1 704 20 B6 红边2 Red edge 2 740 20 B7 红边3 Red edge 3 783 20 B8 近红外 Near-infrared(NIR) 835 10 B8A 窄波近红外 Narrow NIR 865 20 B11 短波红1 Short-wave infrared 1 (SWIR1) 1 614 20 B12 短波红2 Short-wave infrared 2 (SWIR2) 2 202 20 表 2 土地覆盖产品收集情况
Table 2. Collection of land cover products
产品分类 Product classification 发布机构 Issuing authority 数据来源 Data source 产品年份 Product year GLC_FCS 30 中国科学院 Chinese Academy of Sciences Landsat TM/ETM+ 2000、2015、2020 ChinaCover 中国科学院 Chinese Academy of Sciences Landsat TM/ETM+HJ-1A/B 2000、2010、2015 表 3 样本情况
Table 3. Sample plot situation
类型
Type训练样本
Training sample验证样本
Validation sample描述
Description森林 Forest 230 133 非森林 Non-forest 216 80 落叶针叶林 Deciduous coniferous forest 150 98 实地 In the field 88 机载高光谱 Airborne hyperion (CAF-LiCHy) 其他森林 Other forest 163 84 实地 In the field 88 机载高光谱 Airborne hyperion (CAF-LiCHy) 合计 Total 759 571 表 4 光谱特征
Table 4. Spectral characteristics
光谱指数
Spectral index公式
Formula参考文献
ReferenceNDVI (B8 − B4)/(B8 + B4) [20] SAVI (B8 − B4)/(B8 + B4 + 0.5) × 1.5 [21] EVI 2.5 × (B8 − B4)/(B8 + 6.0 × B4 − 7.5 × B2 + 1.0) [22] RVI B8/B4 [23] DVI B8 − B4 [24] 注:NDVI. 归一化植被指数;SAVI. 土壤调整植被指数;EVI. 增强型植被指数;RVI. 比值植被指数;DVI.差值植被指数。Notes: NDVI, normalized difference vegetation index; SAVI, soil-adjusted vegetation index; EVI, enhanced vegetation index; RVI, ratio vegetation index; DVI, difference vegetation index. 表 5 特征统计
Table 5. Statistic of features
特征类型
Feature type特征变量
Feature variables数量
Number光谱波段
Spectral bandB2_5,B3_5,B4_5,B5_5,B6_5,B7_5,B8_5,B8A_5,B11_5,B12_5 30 B2_8,B3_8,B4_8,B5_8,B6_8,B7_8,B8_8,B8A_8,B11_8,B12_8 B2_10,B3_10,B4_10,B5_10,B6_10,B7_10,B8_10,B8A_10,B11_10,B12_10 光谱指数
Spectral indexNDVI_5, DVI_5, RVI_5, EVI_5, SAVI_5 15 NDVI_8, DVI_8, RVI_8, EVI_8, SAVI_8 NDVI_10, DVI_10, RVI_10, EVI_10, SAVI_10 纹理特征
Textural featurecorr, var, idm,con,ent,asm 6 地形特征
Topographic feature海拔 Elevation ,坡度 Slope ,坡向 Aspect 3 合计 Total 54 注:corr. 相关性;var. 方差;idm. 逆差矩;con. 对比度;ent. 熵;asm.角二阶矩。Notes: corr, correlation; var, variance; idm, inverse different moment; con, contrast; ent, entropy; asm, angular second-order moment. 表 6 混淆矩阵
Table 6. Confusion matrix
类别
Type非森林
Non-forest森林
Forest生产精度
Production accuracy/%非森林 Non-forest 75 5 93.75 森林 Forest 3 130 97.74 用户精度
User accuracy/%96.15 96.29 注:总精度96.20%;Kappa系数0.93。Notes: overall accuracy is 96.20%; Kappa coefficient is 0.93. 表 7 机载高光谱数据验证样本混淆矩阵
Table 7. CAF-LiCHy validation of sample confusion matrix
类别
Type其他森林
Other forest落叶针叶林
Deciduous coniferous forest生产精度
Production accuracy/%其他森林
Other forest78 6 92.85 落叶针叶林
Deciduous coniferous forest11 75 87.20 用户精度
User accuracy/%87.64 92.59 注:总精度90.00%;Kappa系数0.80。Notes: overall accuracy is 90%; Kappa coefficient is 0.80. 表 8 实地验证样本混淆矩阵
Table 8. Field validation of sample confusion matrix
类别
Type其他森林
Other forest落叶针叶林
Deciduous coniferous forest生产精度
Production accuracy/%其他森林
Other forest78 6 92.85 落叶针叶林
Deciduous coniferous forest10 88 89.79 用户精度
User accuracy/%88.86 93.61 注:总精度91.20%;Kappa系数0.82。Notes: overall accuracy is 91.20%; Kappa coefficient is 0.82. -
[1] 周以良. 中国的几种植被类型(Ⅵ)落叶针叶林[J]. 生物学通报, 1988(5): 6−10.Zhou Y L. Several types of vegetation in China (Ⅵ) deciduous coniferous forest[J]. Bulletin of Biology, 1988(5): 6−10. [2] 刘旭升, 张晓丽. 森林植被遥感分类研究进展与对策[J]. 林业资源管理, 2004(1): 61−64.Liu X S, Zhang X L. Research advances and counter measures of remote sensing classification of forest vegetation[J]. Forest Resources Management, 2004(1): 61−64. [3] Teluguntla P, Thenkabail P S, Oliphant A, et al. A 30-m landsat-derived cropland extent product of Australia and China using random forest machine learning algorithm on Google Earth Engine cloud computing platform[J]. ISPRS Journal of Photogrammetry and Remote Sensing, 2018, 144: 325−340. doi: 10.1016/j.isprsjprs.2018.07.017 [4] Gorelick N, Hancher M, Dixon M, et al. Google Earth Engine: planetary-scale geospatial analysis for everyone[J]. Remote Sensing of Environment, 2017, 202: 18−27. doi: 10.1016/j.rse.2017.06.031 [5] 李斌, 李崇贵, 李煜. 基于Sentinel-2数据的塞罕坝机械林场落叶松人工林提取[J]. 林业资源管理, 2021(2): 117−123.Li B, Li C G, Li Y. Research on larch extraction in Saihanba Mechanical Forest Farm based on Sentinel-2 data[J]. Forest Resources Management, 2021(2): 117−123. [6] Immitzer M, Vuolo F, Atzberger C. First experience with Sentinel-2 data for crop and tree species classifications in central Europe[J/OL]. Remote Sensing, 2016, 8(3): 166[2023−01−22]. https://doi.org/10.3390/rs8030166. [7] Persson M, Lindberg E, Reese H. Tree species classification with multi-temporal Sentinel-2 data[J/OL]. Remote Sensing, 2018, 10(11): 1794[2023−01−02]. https://doi.org/10.3390/rs10111794. [8] 姚茂林, 江洪, 张丽玉. 基于Sentinel-2影像红边光谱指数与特征优选的竹林提取研究[J]. 海南大学学报(自然科学版), 2022, 40(4): 373−381.Yao M L, Jiang H, Zhang L Y. Bamboo information extraction from Sentinel-2 image based on improved spectral indices and random forest Gini index[J]. Natural Science Journal of Hainan University, 2022, 40(4): 373−381. [9] Immitzer M, Neuwirth M, Böck S, et al. Optimal input features for tree species classification in central Europe based on multi-temporal Sentinel-2 data[J/OL]. Remote Sensing, 2019, 11(22): 2599[2023−01−02]. https://doi.org/10.3390/rs11222599. [10] Grabska E, Frantz D, Ostapowicz K. Evaluation of machine learning algorithms for forest stand species mapping using Sentinel-2 imagery and environmental data in the Polish Carpathians[J/OL]. Remote Sensing of Environment, 2020, 251: 112103[2023−01−23]. https://doi.org/10.1016/j.rse.2020.112103. [11] 郑杨, 董利虎, 李凤日. 黑龙江省红松人工林枝条分布数量模拟[J]. 应用生态学报, 2016, 27(7): 2172−2180.Zheng Y, Dong L H, Li F R. Branch quantity distribution simulation for Pinus koraiensis plantation in Heilongjiang Province, China[J]. Chinese Journal of Applied Ecology, 2016, 27(7): 2172−2180. [12] Shoko C, Mutanga O. Examining the strength of the newly-launched Sentinel 2 MSI sensor in detecting and discriminating subtle differences between C3 and C4 grass species[J]. ISPRS Journal of Photogrammetry and Remote Sensing, 2017, 129: 32−40. doi: 10.1016/j.isprsjprs.2017.04.016 [13] 吴炳方, 苑全治, 颜长珍, 等. 21世纪前十年的中国土地覆盖变化[J]. 第四纪研究, 2014, 34(4): 723−731.Wu B F, Yuan Q Z, Yan C Z, et al. Land cover changes of China from 2000 to 2010[J]. Quaternary Sciences, 2014, 34(4): 723−731. [14] 吴炳方. 中华人民共和国土地覆被地图集(1∶1 000 000)[M]. 北京: 中国地图出版社, 2017.Wu B F. Land cover atlas of the People’s Republic of China (1∶1 000 000)[M]. Beijing: China Cartographic Publishing House, 2017. [15] Zhang X, Liu L, Chen X, et al. Fine land-cover mapping in China using Landsat datacube and an operational SPECLib-based approach[J/OL]. Remote Sensing, 2019, 11(9): 1056[2023−01−02]. https://doi.org/10.3390/rs11091056. [16] Zhang X, Liu L, Chen X, et al. GLC_FCS30: Global Land-Cover product with fine classification system at 30m using time-series Landsat imagery[J]. Earth System Science Data, 2021, 13(6): 2753−2776. doi: 10.5194/essd-13-2753-2021 [17] 庞勇, 蒙诗栎, 史锴源, 等. 中国天然林保护工程区森林覆盖遥感监测[J]. 生态学报, 2021, 41(13): 5080−5092.Pang Y, Meng S L, Shi K Y, et al. Forest coverage monitoring in the Natural Forest Protection Project area of China[J]. Acta Ecologica Sinica, 2021, 41(13): 5080−5092. [18] Pang Y, Li Z, Ju H, et al. LiCHy: the CAF’s LiDAR, CCD and hyperspectral integrated airborne observation system[J/OL]. Remote Sensing, 2016, 8(5): 398[2023−01−02]. https://doi.org/10.3390/rs8050398. [19] 池毓锋, 赖日文, 余莉莉, 等. 基于Landsat 8 OLI数据的树种类型分布提取[J]. 自然资源学报, 2017, 32(7): 1193−1203.Chi Y F, Lai R W, Yu L L, et al. Extracting tree species distribution with Landsat 8 OLI data[J]. Journal of Natural Resources, 2017, 32(7): 1193−1203. [20] Tucker C J. Red and photographic infrared linear combinations for monitoring vegetation[J]. Remote Sensing of Environment, 1979, 8(2): 127−150. doi: 10.1016/0034-4257(79)90013-0 [21] Huete A R. A soil-adjusted vegetation index (SAVI)[J]. Remote Sensing of Environment, 1988, 25(3): 295−309. doi: 10.1016/0034-4257(88)90106-X [22] 董灵波, 梁凯富, 张一帆,等. 基于Landsat 8时间序列数据的翠岗林场森林类型划分[J]. 应用生态学报, 2022, 33(9): 2339−2346.Dong L B, Liang K F, Zhang Y F, et al. Classification of forest types in Cuigang Forest Farm based on time series data of Landsat 8[J]. Chinese Journal of Applied Ecology, 2022, 33(9): 2339−2346. [23] 尹芬, 丁美青. 运用 ENVI 实现 SPOT-5 卫星影像的 RVI 提取[J]. 测绘与空间地理信息, 2016, 39(1): 47−48.Yin F, Ding M Q. RVI extraction of SPOT-5 satellite images using ENVI[J]. Geomatics & Spatial Information Technology, 2016, 39(1): 47−48. [24] 周晓双. 基于高光谱的稻麦叶面积指数监测研究[D]. 南京: 南京农业大学, 2015.Zhou X S. Monitoring leaf area index in rice and wheat with hyperspectral remote sensing[D]. Nanjing: Nanjing Agricultural University, 2015. [25] 李智峰, 朱谷昌, 董泰锋. 基于灰度共生矩阵的图像纹理特征地物分类应用[J]. 地质与勘探, 2011, 47(3): 456−461.Li Z F, Zhu G C, Dong T F. Application of GLCM-based texture features to remote sensing image classification[J]. Geology and Exploration, 2011, 47(3): 456−461. [26] Huang D, Xu S, Sun J, et al. Accuracy assessment model for classification result of remote sensing image based on spatial sampling[J/OL]. Journal of Applied Remote Sensing, 2017, 11(4): 046023[2023−01−02]. https://doi.org/10.1117/1.JRS.11.046023. [27] Qu L, Chen Z, Li M, et al. Accuracy improvements to pixel-based and object-based lulc classification with auxiliary datasets from Google earth engine[J/OL]. Remote Sensing, 2021, 13(3): 453[2023−01−02]. https://doi.org/10.3390/rs13030453. [28] Hill R A, Wilson A K, George M, et al. Mapping tree species in temperate deciduous woodland using time-series multi-spectral data[J]. Applied Vegetation Science, 2010, 13(1): 86−99. doi: 10.1111/j.1654-109X.2009.01053.x [29] Nelson M. Evaluating multitemporal sentinel-2 data for forest mapping using random forest[J/OL]. Environmental Science, Mathematics, 2017[2023−01−02]. https://core.ac.uk/display/132537655. -