GIS Careers |
E-mail lists |
SpatialNews Press Release
Attention Software Developers and Vendors Supporting SDTS Raster Profile
Jump to Website Here
If your software can currently process USGS SDTS DEMS, then it may fail
after October 1, 2001. A non-compliant profile identifier was used in the
USGS SDTS DEMS that were released for vendor software testing, and those
subsequently released to the public at the GeoCommunity GIS Data Depot. If
you coded to our example, and not the FGDC Raster Profile standard, you
unknowingly perpetuated our non-compliant profile identifier string. The
USGS used "SRPE: RASTER PROFILE and EXTENSIONS" in the Identification
module (file xxxxIDEN.DDF). The FGDC compliant value is "SRPE: SDTS RASTER
PROFILE and EXTENSIONS".
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
ftp://sdts.er.usgs.gov/pub/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. If you need further information from the USGS,
please contact the SDTS Task Force at firstname.lastname@example.org.
More Details on the Legacy of the USGS SDTS DEMS
Table 1: Summary of Profile Identifier Variants and SDTS DEM
a) Draft Identifier "SDTS RASTER PROFILE"
Available from USGS EDC GeoData site 1998?6/2001. Contain geopositional
error. Only use integer data type. Approximately 15 million downloads.
b) 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"
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).
Additionally, we provide space on our web site (http://mcmcweb.er.usgs.gov/sdts/implement-priv.html) for developers and
vendors who support SDTS. If you wish to add your product information to
our site please email your request to email@example.com
Hylan Beydler, USGS
National Mapping Program Standards, SDTS Task Force
1400 Independence Road
Rolla, MO 65401
Search GeoCommunity for Related Stories
Search The Web (Google) for Related Stories
Return to Today's News Index
Aug 29, 2001
Jun 26, 2002