Location: Hydrology and Remote Sensing Laboratory
Title: Comparison of different MODIS data product collections over an agricultural area Authors
Submitted to: Geoscience and Remote Sensing Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 30, 2013
Publication Date: January 20, 2014
Citation: Stern, A.J., Doraiswamy, P.C., Hunt, E.R. 2014. Comparison of different MODIS data product collections over an agricultural area. Geoscience and Remote Sensing Letters. 5:1-9. Interpretive Summary: NASA launched two satellites (Terra and Aqua) with the Moderate resolution Imaging Spectroradiometer (MODIS) providing frequent data with large pixel sizes. To better enable scientific and practical applications using MODIS data, teams of scientists created standard data products, which have been revised twice since launch. Two of the data products, leaf area index (LAI) and vegetation type, are important for predicting crop growth and yields regionally and globally. We used field data and a third MODIS data product, land surface reflectance, and determined that the revised LAI data products from NASA were improved compared to earlier versions, but only when data quality assurance flags were used. For small agricultural areas, it may be better to determine LAI from land surface reflectances through model inversion and not use the standard MODIS data products.
Technical Abstract: Standard data products from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) were available at launch (Collection 3) and have undergone two revisions (Collections 4 and 5) during the continuing Terra and Aqua missions. In 2000, a research project was conducted in large fields of corn and soybean to evaluate MODIS leaf area index (LAI) and land cover type (MOD15 and MOD12 data products, respectively) as input to crop yield models. Our objective was to compare Collections 3, 4 and 5 with the ground data to determine data product improvement. Classification of land cover type for collections 3, 4 and 5 were similar to the USDA-NASS Cropland Data Layer. The Collection 5 MOD15 LAI was considerably improved over earlier collections, especially when the quality assurance flags indicated good LAI retrievals. Land surface reflectances (MOD09) of MODIS band 2 (near-infrared, 250-m) were used as inputs to an inversion of the Scattering by Arbitrarily Inclined Leaves (SAIL) model. SAIL-derived LAI was equally correlated to the field data and had less systematic bias in root mean square error compared to the MOD15 LAI products. MODIS data products were designed to address global scientific questions, whereas agricultural applications require data at smaller spatial scales, so inversions of 250-m surface reflectances are better for crop growth and yield models.