GIDS-1 Land Cover (vegetation) Imagery
     
     
     1.0  General Description
     
          The United States Geological Survey (USGS) Earth Resources
     Observation System (EROS) Data Center Land Cover (vegetation) imagery
     is one of several image datasets provided as part of the GEWEX
     Continental-scale International Project (GCIP) Initial Dataset One (GIDS-
     1). The Land Cover imagery covers the conterminous United States.  The
     Land Cover imagery contains monthly composites for a five month period
     encompassing the entire GIDS-1 time period (01 February 1992 through
     30 June 1992).  
     
     2.0  Detailed Data Description
     
          The USGS EROS Data Center routinely ingested 1-km resolution
     satellite data from the Advanced Very High Resolution Radiometer
     (AVHRR) and produced bi-weekly vegetation index imagery.  The
     seasonal land cover regions have unique combinations of vegetation
     mosaics, seasonal properties (onset, peak, and length of green period),
     and annual primary production. The regions are grouped into general land
     cover types; increasing color intensity within each group corresponds to
     increasing primary production. These land cover types include western
     forests, shrublands, alpine tundra, barren, grasslands, croplands, eastern
     forests, coastal wetlands, and water.  For each seasonal land cover region
     there are corresponding sets of attributes of land characteristics
     (vegetation components, seasonal properties, spectral measures, elevation, 
     soils, and climate). The complete land characteristics database, available
     on CD-ROM from the EROS Data Center, can be tailored into classification
     legends or parameters required for specific applications. More information
     regarding these data can be found in Loveland et. al. or by contacting
     Customer Services, USGS, EROS Data Center, Sioux Falls, SD  57198.
     
          The Land Cover imagery were produced monthly from the AVHRR
     data and translated to Graphical Interchange Format (GIF) by the EROS
     Data Center. These GIF images can be viewed using any standard GIF
     display software package. However, any additional detailed information
     from the original files (i.e. pixel reflectivity values, navigation, etc.)
     are not retrievable from the GIF image, but can be obtained from the actual
     data available from EROS. Further general information on GIF files,
     structure and format are provided in the References.
     
     
     3.0  Quality Control Processing
     
          No additional quality control or re-navigation was performed on
     the imagery by the UCAR/Office of Field Project Support (OFPS). 
     
     4.0  References
     
     Kay: Graphics File Formats, 2/E.  ISBN: 0-07-034025-0, McGraw Hill.
     
     Loveland, T.R, J.W. Merchant, D.O. Ohlen, and J.F. Brown, 1991:
          Development of a Land-cover Characteristics Database for the
          Conterminous United States. Photogrammetric Engineering &
          Remote Sensing, Vol 57, No. 11,    November 1991, 
          pp. 1453-1463.
     
     Luse, M: Bitmapped Graphics Programming in C++. ISBN: 0-201-
          63209-8, Addison-Wesley.