eMODIS ALASKA

摘要

Operational monitoring of Alaskan vegetation using remote sensing data is a challenging project due to a general lack of consistency and coverage from historical and existing platforms. With a more frequent repeat cycle than Landsat and higher spatial resolutions than the Advanced Very High Resolution Spectroradiometer (AVHRR), the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS) Moderate Resolution Imaging Spectroradiometer (MODIS) is a desirable data source for Alaska. For operational monitoring however, the benefits of MODIS are counteracted by usability issues with the standard map projection, file format, composite interval, high-latitude "bow-tie" effects, and production latency. eMODIS Alaska responds to a community-specific need for alternatively packaged EOS-Terra MODIS data, addressing each of these factors for historical trend analysis. Produced at the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center, eMODIS delivers Normalized Difference Vegetation Index (NDVI) and surface reflectance over Alaska, extending into Canada to cover the Yukon River Basin (YRB). eMODIS products are composited over 7-day weeks during the growing season (February - October). Each 250-meter (m), 500-m, and 1,000-m composite represents the entire geographic region on the Alaska Albers Equal Area mapping grid and is distributed in Geostationary Earth Orbit Tagged Image File Format (GeoTIFF). eMODIS enhancements include the implementation of a sun angle threshold (83 deg) and use of a snow filter to tag snowy pixels when no others are available. A simple File Transfer Protocol (FTP) distribution site is currently enabled on the Internet for direct download of eMODIS products (ftp://elpdl02.cr.usgs.gov/eMODIS).