Investigating collection 4 versus collection 5 MODIS 250 m NDVI time-series data for crop separability in Kansas,USA

The primary objective of this research was to analyse collection 5 versus collection 4 time-series normalized difference vegetation index (NDVI) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) 250 m for the purpose of separating crop types. Using extensive ground reference data from the state of Kansas in the central USA, NDVI value profiles were extracted from different collection versions for 2001 (collections 4 and 5) and 2005 (collection 5 only). Phenological curves for all crops and all data sets were created and visually inspected. Jeffries–Matusita (J-M) distance statistical analysis was performed to assess crop separability. Contrary to expectations, collection 5 time-series MODIS 250 m NDVI data were found to be inferior to collection 4 with respect to crop separability. Specifically, collection 4 data exhibited a greater dynamic range across the growing seasons of the various crop types, and this discriminatory advantage was supported by J-M distance analysis. Though the analysis did not suggest reasons for the outcome, it corroborates the conclusion of the only other similar study in the literature comparing data from collections 4 and 5. Considering the pervasive use of these data for land-cover mapping, it is recommended that MODIS NDVI data from collection 4 should be used where possible for crop type mapping in agricultural regions with climate, geography, and crops similar to Kansas.