Image Scene Selection and Data Preprocessing

Scene selection is driven by the MTBS fire history database. Scenes are selected using the Global Visualization Image Selection (GLOVIS) browser developed by USGS-EROS (http://glovis.usgs.gov/). Enhancements were made to GLOVIS specifically to facilitate the magnitude of scene selection effort required for this project. These enhancements, available to all GLOVIS users, include the ability to incorporate ESRI ARCGIS shape files in the viewer to aid scene selection and scene specific Advanced Very High Resolution Radiometer (AVHRR) greenness graphs for determining peak periods of photosynthetic activity, or peak-of-green periods. The fire history shapefile, specific to an MTBS mapping zone, is loaded into the viewer, and analysts use fire locations to guide scene selection for each fire. Prefire and postfire images are selected for each incident. Scenes selected for fires that will be processed as an extended assessment are based on peak-of-green condition or as close as cloud-free data are obtainable. Limitations in data availability due to atmospheric conditions will naturally compromise selections for fires in areas prone to summer and fall cloud and smoke obscurity. Northern latitudes will also be subject to a shorter period of optimal scene selection due to undesirable sun angles in the fall.

Selected scenes are ordered and processed according to existing USGS-EROS protocols. Image data are geometrically (including terrain correction) and radiometrically corrected through the NLAPS process. Image data are delivered to EROS and RSAC analysts to be processed into fire severity information. Landsat image data acquired for this project will become part of the national image archive and will be available at NLCD archive costs. Current estimates expect an increase in available archive data of more than 7000 scenes. The existing USGS Multi-Resolution Land Characteristics image archive (http://www.mrlc.gov/), available through several existing Web portals, (e.g., GLOVIS), will be the primary repository for these data.