SDTS - Open Source Mapping

"SDTS" is a container file format used by the USGS for its GIS data. For this project these data sets are used to build the base layers for the trail maps.

Page Contents

SDTS Data Types
Getting the SDTS Data

DLG Data Source
DEM Data Source

Organizing SDTS Data

SDTS Data Types

The SDTS data are organized corresponding to the USGS's 7.5 min and 15 min topographic maps. For each topographic map the SDTS data are divided into two distinct types of data sets.

Digital Elevation Model or DEM are rectangular grids of elevation points. DEM are used for elevation data alone.
Digital Line Graphics or DLG are line drawings of hydrographic, political boundries, and transportation features.

DEM
As an example the SDTS DEM file for the Glasgow 7.5 min topographic map is 1694514.DEM.SDTS.TAR.GZ. The "TAR.GZ" suffix marks this file as a compressed archieve file that when open contains the individual files:

9941CATD.DDF	9941DDOM.DDF	9941DQHL.DDF	9941IREF.DDF	9941STAT.DDF
9941CATS.DDF	9941DDSH.DDF	9941DQLC.DDF	9941LDEF.DDF	9941XREF.DDF
9941CEL0.DDF	9941DQAA.DDF	9941DQPA.DDF	9941RSDF.DDF
9941DDDF.DDF	9941DQCG.DDF	9941IDEN.DDF	9941SPDM.DDF

The starting point for this set is the 9941CELO.DDF file.

DLG
The DLG files for the same Glasgow topo are: 1174412.HY.sdts.tar.gz for hydrographic data and, 1204942.RD.sdts.tar.gz, 1386980.HP.sdts.tar.gz, 1204819.MT.sdts.tar.gz, 1205062.RR.sdts.tar.gz for roads and other "transportation features". Each of these again unpacks into a large number of files. It is recommended to unpack each of these into its own sub-directory.

The data type, archive file, and starting points are sumerized in the table.

Data Type	Archive Container	Starting File
Elevation	1694514.DEM.SDTS.TAR.GZ	9941CEL0.DDF
Roads	1204942.RD.sdts.tar.gz	RD/TR01LE01.DDF
Utilities	1204819.MT.sdts.tar.gz	MT/TR01LE01.DDF

Getting the SDTS Data

DLG Data Source

The DLG data for the 1:24,000 scale maps are available on-line directly from the USGS. The site has tree of links descending to levels of finer detail:

Country Wide

State(Virginia)

Quadrangle(Glasgow)

DEM Data Source

The DEM data is a little more complicated becuase the USGS has contracted with comercial vendors who distribute the data both as a free services and as a value-added, for-fee service. The free downloads come with the requirement of signin onto there mailing list. The current comercial vendors are:

Using the server geo community, the path to the data selection is

Select state

Select County

Select Map Scale and type

Select quadrangle

Organizing SDTS Data

The images below show a typical orgainization of the complete data set for a given map, Buena Vista in this example.

STDT Tar Files	Data set folder	Road Sub-folder