Winter wheat planting area extraction based on MODIS EVI image time series

The vegetation index time series can reflect the growth changes of the vegetation in the time dimension, and this provides a potential way for the land cover classification and cropland area extraction. The field survey data were used to extract sample and validate for MODIS EVI data indirectly by using TM data as the transition data. Considering the winter wheat phenological calendar, the identifiers of winter wheat were parameterized as growth rate, declining rate, ratio of peak to dormancy, and then the winter wheat area of Huabei Plain was extracted. The extraction result was quite consistent with TM-based result with a precision of 89.13%. For the whole Huabei Plain, twelve out of 13 selected counties/cities had errors less than 20% than those from the official statistics data. The errors were caused mostly by the coarse resolution of MODIS and the smaller area of cropland of Huabei Plain.