SDTS stands for Spatial Data Transfer Standard. SDTS was a standard for transferring earth-referenced spatial data across disparate computer programs. The U.S. Geological Survey (USGS) released SDTS after twelve years of development and testing in 1992 and was subsequently approved as Federal Information Processing Standard (FIPS) Publication 173, known as FIPSPUB 173-1, 1994. The FIPS version has been superceded by current version, known as ANSI NCITS 320-1998 and was ratified by the American National Standards Institute (ANSI) June 9, 1998.
The file extension for a SDTS file is .DDF although multi module files contain chronologically alphabetical extensions such as .DDG and .DDH. Many commercial GIS software programs such as Esri’s ArcInfo and ArcView as well as MapInfo came with either native capabilities or extensions that allow for the importation of SDTS files. Third party translators such as the public and freely available sdts2dem (developed by Sol Katz of the Bureau of Land Management) could translate SDTS back to a “native” DEM format.
Compliance with SDTS was made mandatory for federal agencies and the format was made available for use by available for use by state and local governments, the private sector, and research and academic organizations.
The demise of SDTS was almost universally despised for its cumbersomeness and difficulty in converting SDTS data to a usable GIS data format. Gregg Townsend from the Department of Computer Science at the University of Arizona, stated in 2002 that the “adoption of SDTS was a giant step backwards.” A paper by several scientists from the USGS published in the International Journal of Geographical Information Science (IJGIS Theme Issue on Interoperability, Volume 12 Number 4, June 1998) stated:
The Spatial Data Transfer Standard (SDTS) was designed to be capable of representing virtually any data model, rather than being a prescription for a single data model. It has fallen short of this ambitious goal for a number of reasons.”
In the paper, barriers to the successful implementation of SDTS were outlined:
- complexity of SDTS;
- slowness in the development of practical SDTS profiles;
- restriction of each SDTS dataset to a single profile;
- lack of a clear definition of geospatial features in SDTS; and
- ambiguity in the means of specifying cardinality of relationships in a data model.
As of February, 2010, USGS web pages about the SDTS standard all now bear at the top of each page in bold red type the following: “Note: The information on this page is being retained for technical and historical reference only. The site is not under active maintenance and may include expired information and outdated links.” No official information on the elimination of SDTS as a standard is available although new releases of USGS data such as the Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010) do not have SDTS file downloads.