Application of MODIS/NDVI and MODIS EVI to extracting the information of cultivated land and comparison analysis

MODIS vegetation index is one of the important data for extracting the information of cultivated land. In order to compare the application of the two critical vegetation indexes (NDVI/EVI) in the information extraction, the authors took Oasis in Hexi Corridor Region as experimental area, reconstructed the MODIS/EVI and MODIS/NDVI(16 day, 250m) time series in 2006 in the test area by HANTS(Harmonic Analysis of Time Series). Then, the cultivated land and fallow land were identified; multiple cropping index and the type of the crop were extracted. Based on those, the behaviors of MODIS/EVI and MODIS/NDVI were compared. Results indicate that: (1) by using HANTS, the researchers could get the EVI/NDVI harmonic curves, the mean VIs and the amplitude of the harmonics which then were utilized in the identification of the cultivated land, and EVI appeared to be more precise, with the overall accuracies of 97.17% and 95.99% and Kappa coefficients of 0.7938 and 0.6518, respectively. (2) Multiple cropping index was extracted by counting the number of the curve’s peak; and when the threshold of the peak value of the NDVI and EVI curves were set as 0.25 and 0.20, respectively, the fallow land could be well figured out. (3) From harmonic curves, some eigenvalues, such as time of the maximum growth rate, time of peak and the value of peak can be extracted, based on which the crop types can be primarily distinguished. And EVI still performed better than NDVI in this section.