SDTS Raster Profile
The Spatial Data Transfer Standard (SDTS) is a standard that defines a general, non proprietary format for the distribution and archiving of vector and raster spatial data with attributes, metadata, a data quality report, and usually a data dictionary. The SDTS is a standard that many federal agencies in the United States use, or have used, for the archival and distribution of spatial data sets.
SDTS is a very general standard with provisions that allow it to support virtually any type of spatial data. Because of this, a single program cannot be expected to ingest data from an arbitrary SDTS file set. Instead, there are well-defined conventions for encoding specific types of data in SDTS format, called profiles. Profiles are essentially special cases of SDTS. Some common SDTS profiles are the Raster Profile (for raster data such as DEMs), the Topological Vector Profile (for many types of vector data), and the Point Profile (for high-precision geodetic control and survey points).
In 1998, the US Geological Survey (USGS) began distributing some of their spatial data holdings in this new format. In particular, they converted all of their high-resolution 7.5-minute DEMs (UTM, 30 meter pixels) to the SDTS Raster Profile format and made them available on the Internet for free download. They also converted their 1:24K Digital Line Graph (DLG) data, which have a comparable resolution, to the SDTS Topological Vector Profile format. RiverTools can read and display data in both of these formats. An SDTS transfer typically consists of many separate files with the extension ".DDF". The data in these files conforms to the ISO 8211 data exchange standard. They are often bundled and compressed into a single file for distribution. The raster or vector data is typically contained in just one of the files, while the remaining files tend to be small and contain various types of metadata. An SDTS Raster Profile DEM consists of about 18 files, with the elevation data in a file that has the extension *CEL0.DDF. Questions about SDTS should be sent to email@example.com.
Starting in July 2001, the USGS stopped distributing 7.5-minute DEMs in the SDTS Raster Profile format from their website and instead began to authorize private companies to act as distributors of this data. In June 2003, the USGS had partnered with three such companies: Geocomm International Corp., ATDI, and MapMart.com (see links below). Each has a website that allows the data to be downloaded for free, although download speed is purposely slowed in some cases. The data given to these companies by the USGS had some slight differences in formatting such that most software that had supported the SDTS Raster Profile format prior to that time would not import the new data without application of a patch or service pack.
Raster Profile DEMs and Topological Vector Profile DLGs are available from the EROS Data Center of the US Geological Survey (USGS).
7.5-minute DEMs (UTM, 30 meter pixels) for the entire US in SDTS Raster Profile format are available and can be downloaded free of charge from the companies mentioned above. It is expected that Shuttle Radar Topography Mission (SRTM) data will also be distributed in SDTS Raster Profile format by the USGS.
USGS SDTS Page: http://mcmcweb.er.usgs.gov/sdts
EROS Data Center: http://edc.usgs.gov/
USGS Statement: http://edc.usgs.gov/geodata/
USGS Earth Explorer: http://earthexplorer.usgs.gov
DEMs - GIS Data Depot: http://data.geocomm.com/dem/
DEMs - ATDI: http://www.atdi-us.com/
DEMs - MapMart.com: http://www.mapmart.com/DEM.htm
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