Monitoring of spatial\|temporal change of winter wheat area in Guanzhong Region based on Google Earth Engine
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DOI:10.7606/j.issn81000-7601.2020.03.36
Key Words: remote sensing  winter wheat planting area  spatial\|temporal change  MODIS NDVI  Google Earth Engine  Guanzhong Region
Author NameAffiliation
GUO Xin College of Water Conservancy and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China 
WANG Naijiang College of Water Conservancy and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China 
ZHANG Lingling Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China 
GUO Yongqiang College of Water Conservancy and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China 
CHU Xiaosheng College of Water Conservancy and Architectural Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China 
FENG Hao Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi 712100, China
Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China 
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Abstract:
      A method based on Google Earth Engine (GEE) was developed and tested in this study for mapping winter wheat planting area over Guanzhong Region. After analyzing the winter wheat MODIS NDVI time series curve and its phenology calendar in Guanzhong Region, the extraction model was established based on NDVI remodel amplification and NDVI increase/decrease slope threshold. The result showed that area of winter wheat extracted by remote sensing agreed well with statistics, with the determination coefficient R2 of 0.82 and 0.62, and the index of agreement d of 0.95 and 0.84 at city level and county level, respectively. Further, the spatial consistency accuracy of extraction results and field survey data was 93.4%. Winter wheat was mainly distributed on Guanzhong Plain, whose terrain is relatively flat. In 2011-2017, winter wheat planting area in Guanzhong Region was showing a downward trend. There was a series decline by 8.47% (83.22×103hm2) in planting area of winter wheat in 7 years. In this study, the peak and valley of NDVI curve were considered as never before. This study can serve as a reference for large\|scale and long\|time monitoring of spatial and temporal information of winter wheat planting area with remote sensing data.