Increasing the Accuracy of Mapping Urban Forest Carbon Density by Combining Spatial Modeling and Spectral Unmixing Analysis
Accurately mapping urban vegetation carbon density is challenging because of complex landscapes and mixed pixels. In this study, a novel methodology was proposed that combines a linear spectral unmixing analysis (LSUA) with a linear stepwise regression (LSR), a logistic model-based stepwise regressi...
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doaj-65c3791cea434e2eaeeb67238e5212f92020-11-24T22:23:06ZengMDPI AGRemote Sensing2072-42922015-11-01711151141513910.3390/rs71115114rs71115114Increasing the Accuracy of Mapping Urban Forest Carbon Density by Combining Spatial Modeling and Spectral Unmixing AnalysisHua Sun0Guangping Qie1Guangxing Wang2Yifan Tan3Jiping Li4Yougui Peng5Zhonggang Ma6Chaoqin Luo7Research Center of Forestry Remote Sensing and Information Engineering, Central South University of Forestry and Technology, Changsha 410004, ChinaDepartment of Geography, Southern Illinois University at Carbondale, Carbondale, IL 62901, USAResearch Center of Forestry Remote Sensing and Information Engineering, Central South University of Forestry and Technology, Changsha 410004, ChinaXianhu Botanic Garden of Shenzhen, Shenzhen 518004, ChinaResearch Center of Forestry Remote Sensing and Information Engineering, Central South University of Forestry and Technology, Changsha 410004, ChinaCollege of Forestry, South China Agricultural University, Guangzhou 510642, ChinaResearch Center of Forestry Remote Sensing and Information Engineering, Central South University of Forestry and Technology, Changsha 410004, ChinaResearch Center of Forestry Remote Sensing and Information Engineering, Central South University of Forestry and Technology, Changsha 410004, ChinaAccurately mapping urban vegetation carbon density is challenging because of complex landscapes and mixed pixels. In this study, a novel methodology was proposed that combines a linear spectral unmixing analysis (LSUA) with a linear stepwise regression (LSR), a logistic model-based stepwise regression (LMSR) and k-Nearest Neighbors (kNN), to map the forest carbon density of Shenzhen City of China, using Landsat 8 imagery and sample plot data collected in 2014. The independent variables that contributed to statistically significantly improving the fit of a model to data and reducing the sum of squared errors were first selected from a total of 284 spectral variables derived from the image bands. The vegetation fraction from LSUA was then added as an independent variable. The results obtained using cross-validation showed that: (1) Compared to the methods without the vegetation information, adding the vegetation fraction increased the accuracy of mapping carbon density by 1%–9.3%; (2) As the observed values increased, the LSR and kNN residuals showed overestimates and underestimates for the smaller and larger observations, respectively, while LMSR improved the systematical over and underestimations; (3) LSR resulted in illogically negative and unreasonably large estimates, while KNN produced the greatest values of root mean square error (RMSE). The results indicate that combining the spatial modeling method LMSR and the spectral unmixing analysis LUSA, coupled with Landsat imagery, is most promising for increasing the accuracy of urban forest carbon density maps. In addition, this method has considerable potential for accurate, rapid and nondestructive prediction of urban and peri-urban forest carbon stocks with an acceptable level of error and low cost.http://www.mdpi.com/2072-4292/7/11/15114forest carbonintegrationLandsat 8 imagek-nearest neighborsmappingmixed pixelregressionShenzhen Cityvegetation fraction |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Hua Sun Guangping Qie Guangxing Wang Yifan Tan Jiping Li Yougui Peng Zhonggang Ma Chaoqin Luo |
spellingShingle |
Hua Sun Guangping Qie Guangxing Wang Yifan Tan Jiping Li Yougui Peng Zhonggang Ma Chaoqin Luo Increasing the Accuracy of Mapping Urban Forest Carbon Density by Combining Spatial Modeling and Spectral Unmixing Analysis Remote Sensing forest carbon integration Landsat 8 image k-nearest neighbors mapping mixed pixel regression Shenzhen City vegetation fraction |
author_facet |
Hua Sun Guangping Qie Guangxing Wang Yifan Tan Jiping Li Yougui Peng Zhonggang Ma Chaoqin Luo |
author_sort |
Hua Sun |
title |
Increasing the Accuracy of Mapping Urban Forest Carbon Density by Combining Spatial Modeling and Spectral Unmixing Analysis |
title_short |
Increasing the Accuracy of Mapping Urban Forest Carbon Density by Combining Spatial Modeling and Spectral Unmixing Analysis |
title_full |
Increasing the Accuracy of Mapping Urban Forest Carbon Density by Combining Spatial Modeling and Spectral Unmixing Analysis |
title_fullStr |
Increasing the Accuracy of Mapping Urban Forest Carbon Density by Combining Spatial Modeling and Spectral Unmixing Analysis |
title_full_unstemmed |
Increasing the Accuracy of Mapping Urban Forest Carbon Density by Combining Spatial Modeling and Spectral Unmixing Analysis |
title_sort |
increasing the accuracy of mapping urban forest carbon density by combining spatial modeling and spectral unmixing analysis |
publisher |
MDPI AG |
series |
Remote Sensing |
issn |
2072-4292 |
publishDate |
2015-11-01 |
description |
Accurately mapping urban vegetation carbon density is challenging because of complex landscapes and mixed pixels. In this study, a novel methodology was proposed that combines a linear spectral unmixing analysis (LSUA) with a linear stepwise regression (LSR), a logistic model-based stepwise regression (LMSR) and k-Nearest Neighbors (kNN), to map the forest carbon density of Shenzhen City of China, using Landsat 8 imagery and sample plot data collected in 2014. The independent variables that contributed to statistically significantly improving the fit of a model to data and reducing the sum of squared errors were first selected from a total of 284 spectral variables derived from the image bands. The vegetation fraction from LSUA was then added as an independent variable. The results obtained using cross-validation showed that: (1) Compared to the methods without the vegetation information, adding the vegetation fraction increased the accuracy of mapping carbon density by 1%–9.3%; (2) As the observed values increased, the LSR and kNN residuals showed overestimates and underestimates for the smaller and larger observations, respectively, while LMSR improved the systematical over and underestimations; (3) LSR resulted in illogically negative and unreasonably large estimates, while KNN produced the greatest values of root mean square error (RMSE). The results indicate that combining the spatial modeling method LMSR and the spectral unmixing analysis LUSA, coupled with Landsat imagery, is most promising for increasing the accuracy of urban forest carbon density maps. In addition, this method has considerable potential for accurate, rapid and nondestructive prediction of urban and peri-urban forest carbon stocks with an acceptable level of error and low cost. |
topic |
forest carbon integration Landsat 8 image k-nearest neighbors mapping mixed pixel regression Shenzhen City vegetation fraction |
url |
http://www.mdpi.com/2072-4292/7/11/15114 |
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