Increasing the Accuracy of Mapping Urban Forest Carbon Density by Combining Spatial Modeling and Spectral Unmixing Analysis

Remote Sensing

Hua Sun¹  Guangping Qie⁴  Guangxing Wang³  Yifan Tan²  Jiping Li¹  Yougui Peng⁵  Zhonggang Ma¹  Chaoqin Luo¹  Dengsheng Lu³  Guomo Zhou³  Conghe Song³  Alfredo R. Huete³ 

[1] Research Center of Forestry Remote Sensing and Information Engineering, Central South University of Forestry and Technology, Changsha 410004, China; E-Mails:;Xianhu Botanic Garden of Shenzhen, Shenzhen 518004, China; E-Mail:Research Center of Forestry Remote Sensing and Information Engineering, Central South University of Forestry and Technology, Changsha 410004, China;;Department of Geography, Southern Illinois University at Carbondale, Carbondale, IL 62901, USA; E-Mail:;College of Forestry, South China Agricultural University, Guangzhou 510642, China; E-Mail:

关键词: forest carbon;    integration;    Landsat 8 image;    k-nearest neighbors;    mapping;    mixed pixel;    regression;    Shenzhen City;    vegetation fraction;   

DOI  :  10.3390/rs71115114

来源: mdpi

【 摘 要 】

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.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.