A new methodology to map double-cropping croplands based oncontinuous wavelet transform

Cropping intensity is one of the major factors in crop production and agricultural intensification. A newdouble-cropping croplands mapping methodology using Moderate Resolution Imaging Spectroradiome-ter (MODIS) time series datasets through continuous wavelet transform was proposed in this study. Thismethodology involved four steps. First, daily continuous MODIS Enhanced Vegetation Index (EVI) timeseries datasets were developed for the study year. Next, the EVI time series datasets were transformedinto a two dimensional (time-frequency) wavelet scalogram based on continuous wavelet transform.Third, a feature extraction process was conducted on the wavelet scalogram, where the characteristicspectra were calculated from the wavelet scalogram and the feature peak within two skeleton lines wasobtained. Finally, a threshold was determined for feature peak values to discriminate double-croppingcroplands within each pixel. The application of the proposed procedure to China's Henan Province in2010 produced an objective and accurate spatial distribution map, which correlated well with in situobservation data (over 90% agreement). The proposed new methodology efficiently handled complexvariability that might be caused by regional variation in climate, management practices, growth peaksby winter weed or winter wheat, and data noise. Therefore, the methodology shows promise for futurestudies at regional and global scales.