Multisensor comparisons for validation of MODIS vegetation indices

Vegetation indices (VI) are one of the standard science products available from the Moderate Resolution Imaging Spectroradiometer (MODIS). Validation of MODIS-VI products was an important prerequisite to using these variables for global modeling. In this study, validation of the MODIS-VI products including single-day MODIS, level 2 (gridded) daily MODIS surface reflectance (MOD09), 16-day composited MODIS (MOD13) was performed utilizing multisensor data from MODIS, Thematic Mapper (TM), and field radiometer, for a rice-planting region in southern China. The validation approach involved scaling up independent fine-grained datasets, including ground measurement and high spatial resolution imagery, to the coarser MODIS spatial resolutions. The 16-day composited MODIS reflectance and VI matched well with the ground measurement reflectance and VI. The VI of TM and MODIS were lower than the ground VI. The results demonstrated the accuracy, reliability, and utility of the MODIS-VI products for the study region.