Accounting for error propagation in the development of a leaf area index (LAI) reference map to assess the MODIS MOD15A2 LAI product

The ability to effectively use remotely sensed data for environmental analysis is dependent on understanding the underlying procedures and associated variances attributed to the data processing and image analysis technique. Equally important is understanding the error associated with the reference data used to assess the accuracy of image products. This paper details measurement variance accumulated in the development of a leaf area index (LAI) reference maps used to assess the accuracy of the Moderate Resolution Imaging Spectroradiometer (MODIS) MOD15A2 LAI 1000-m product in the southeastern United States. MODIS LAI was compared with reference data derived from Landsat Enhanced Thematic Mapper (ETM+) during the 2002 field season in the Albemarle-Pamlico Basin in south-central Virginia. Ground-based optical LAI estimates, at scales ranging between 1-m to 100-m, were correlated with various ETM+ derived vegetation indices at a 30-m pixel resolution. These 30-m pixels were scaled up to the 1000-m MODIS LAI pixel resolution and averaged to give one LAI value. A detailed listing of error propagation for this reference data set includes uncertainty associated with: (1) integrated optical LAI field estimating technique combining the Tracing Radiation and Architecture of Canopies (TRAC) instrument and hemispherical photography, (2) the classification of ETM+ into land-cover components, and (3) the scaling of this 30-m classified data into MODIS (1000-m x 1000-m) scale resolution. This paper has been reviewed in accordance with the United States Environmental Protection Agency’s peer and administrative review policies and approved for presentation and publication.