Web-Enabled Landsat Data (WELD): A Consistent, Long-Term, Large-Area, 30m Data Record For The Terrestrial User Community

摘要

Since January 2008, the U.S. Geological Survey has been providing free terrain-corrected and radiometrically calibrated Landsat data via the Internet This revolutionary data policy provides the opportunity to use all the data in the U.S. Landsat archive and to consider the systematic utility of Landsat data for long-term large-area monitoring. The NASA funded Web-enabled Landsat Data (WELD) project is systematically generating 30m weekly, monthly, seasonal, and annual composited Landsat Enhanced Thematic Mapper Plus (ETM+) mosaics of the conterminous United States and Alaska from 2005 to 2012. The WELD products are developed specifically to provide consistent data that can be used to derive land cover as well as geophysical and biophysical products for regional assessment of surface dynamics and to study Earth system functioning. The products are processed so that users do not need to apply the equations and spectral calibration coefficients and solar information to convert the ETM+ digital numbers to reflectance and brightness temperature, and successive products align precisely, making them simple to use for multi-temporal applications. The consistency and quality of the ETM+ data will be improved through a fusion with standard MODIS land products, including the MODIS BRDF reflectance anisotropy product to radiometrically normalize and fill missing (cloudy and SLC-off) Landsat pixels and using MODIS atmospheric characterization data to systematically atmospherically correct the Landsat data. Information on the WELD products, how to access them via the Internet, and preliminary examples of prototype global WELD 30m products are presented.