New vegetation condition images are created every week during the crop season. Historically, they were created every two weeks. These images are in GIF format, type GIF87A. The images are 256 color (8-bit) GIF's created using a 1024x768 screen resolution (viewing at 640x480 will cause further sampling). The images are derived directly from postscript print files intended for 11"x17" color prints; they are approximately 300 - 500K bytes in size.
Starting in 1999, the images for the entire US (NDVI, Ratio/Previous, and Ratio/Median - as available) for a given period are also being created in an Adobe PDF format. The PDF format allows for browsing user-defined areas and zooming in more closely to view them. The PDF files were created with 256 colors for printing on 8.5"x11" size paper. Anyone with a standard Acrobat reader will be able to view the files. The PDF images have a higher resolution that the GIF files, but are also much larger; PDF images may be as large as 2.0MB.
Starting with the 2004 season, the entire US NDVI composite for each period has been or will be converted to a GeoTiff image for use in geographic information systems software. (2011 will be loaded as available). Due to the size of these files (13-14 MB), each GeoTiff has been compressed into a "Tar" format file for easier download (4-5 MB). Select the "Download" option above to access these tiff files. Standard products are selectable below:
For more information about this topic
or about the NASS Spatial Analysis Research Section (SARS), contact the
GeoSpatial Information Branch at HQ_RDD_GIB@nass.usda.gov.
Last Modified: 04/09/2012