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The compliant USGS SDTS DEMS will be available from the GIS Data Depot to the public circa October 1, 2001. Sample test datasets are at http://thor-f5.er.usgs.gov/sdts/datasets/raster/dem. The FGDC Raster Profile is at http://www.fgdc.gov/standards/documents/standards/sdts_pt5/.
The USGS sincerely appreciates your efforts to promote FGDC standards. We encourage you to modify, retest, and announce to your users about the need for the software change.
b) USGS typo "SRPE: RASTER PROFILE and EXTENSIONS"
USGS typo "SRPE: RASTER PROFILE and EXTENSIONS" Available from GIS Data Depot 7/2001-9/2001. Contain incorrect profile identifier. Includes decimeter DEMs with binary floating point elevation values. Approximately 50,000 downloads.
c) FGDC Profile Identifier "SRPE: SDTS RASTER PROFILE and EXTENSIONS"
FGDC Profile Identifier "SRPE: SDTS RASTER PROFILE and EXTENSIONS" Available from GIS Data Depot beginning 10/2001 contain correct profile identifier. Note in README explains which errors are fixed, so customers know when they have corrected data.
In 1997, the 7.5-minute DEM holdings were converted en mass to the draft form of the SDTS Raster Profile (Table 1a). These DEMs were distributed free from the EDC GeoData Web/FTP site from 1998 through June 2001. These SDTS DEMs contain the draft profile identifier of "SDTS Raster Profile". In providing technical support to our data customers, we discovered a geopositional error that was introduced during the conversion. The elevation values were not affected, but the post position could be off as much as 30 meters horizontally. This affected some applications, but not all. There were approximately 15 million SDTS DEMs downloaded.
In February 2001, the 7.5-minute DEM holdings were converted en mass to the ratified FGDC SDTS Raster Profile (Table 1b). Changes included: 1) A new profile identifier; 2) a new elevation data type of binary floating point*; 3) a corrected geopositional conversion; and, 4) improved metadata regarding data quality. These DEMS are being distributed from the GeoCommunity GIS Data Depot site as of July 2001.
In August 2001, the 7.5-minute DEM holdings will be converted en mass using the correct profile identifier (Table 1c). These DEMs will be distributed from the GeoCommunity GIS Data Depot site circa October 2001. Check the web site for the current status.
* The DEM product changed to decimal units for the elevation values so most DEMs made after 1999 use a data type of floating point (i.e. 810.25) rather than the previous integer type (i.e. 850).
U.S. Department of the Interior
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