Before starting any work, it is easier to download all the files used in the conversion steps. They come from a variety of sites; Internet address, file names, and links can be found below. A standard browser can be used to download files from any of the sites, including the FTP sites.
Getting the files you need
USGS EROS Data Center: ftp://edcftp.cr.usgs.gov/pub/data/
This site contains the SDTS data files, both the master data dictionary files and the
specific data files for each quad. There is a README file that gives site specific
guidance. You need the following files from this site:
1- 00MasterDD_LRG_SDTS_tar.zip (master data dictionary for 1:24,000 data)
2- Desired data file(s); these are organized alphabetically, by quad name, with the
following conventions:
SDTS transfers are stored as compressed "tar" archive files. Each transfer
contains a complete set of files, for a specific layer and version, covering a quadrangle.
The transfer naming convention is as follows:
XXX.layer.V.sdts.tar.gz.
- XXX = unique quadrangle identifier which consists of quad SE coordinates preceded
by a D
- layer = data category name abbreviation (such as bd for boundary) followed by 0
(zero) and "s " (for 7.5 minute) or "f" (for 15 minute)
- V = file version (1-current, 2-historic)
- SDTS = denotes that the data is in SDTS format
- tar = represents "tar" file
- gz = refers to the "gzip" compression
USGS Midcontinent Data Center: Arc/Info AML overview page on SDTS site - check here for any changes or new information.
Documentation is at http://thor-f5.er.usgs.gov/sdts/software/dlg3/ . You will need the file for the DLG-3 SDTS Transfer Description manual, describing in detail the .ddf modules and attribute codes. It is called dlg3sdts.wp.
The Arc/Info AML for converting SDTS data to a coverage and relating the attribute data in one step along with related files is also at this site, at http://thor-f5.er.usgs.gov/sdts/software/tools/arc_aml/ . Download the file sdts2cov.zip and you will have the aml, the file sdts2cov.readme, and entdef.e00. The readme file will take you through the process step by step - read it first !
File Locations:
Before uncompressing the files you will need to have a directory set up called masterdd containing the Master Data Dictionary. The masterdd directory should be in the same location as the sdts data directories. For example, if you have created an ARC/INFO workspace called chicago there should be within the workspace a separate directory for each SDTS transfer along with the master data dictionary. Each of these directories contains .DDF files.
Sample Structure
Directory (workspace) - chicago
Subdirectories - chicbound
chichydro
chichypso
masterdd
The aml and the file entdef.e00 should be placed in the chicago (workspace) directory. This file contains entity definitions used in the conversion to label attributes with recognizable descriptions.
Uncompressing the data
There are a number of ways to extract or uncompress the files. WinZip used with the "TAR file Smart CR/LF conversion" turned off will work. Another option is to use gunzip with the -d option, then tar with the -vxf option to decompress and extract the files. See http://www.fws.gov/data/gisconv/gisconv.html for more detailed directions on that method. Please note - at least some versions of gunzip will not deal with long UNIX names; you need to rename the file using an 8.3 DOS naming convention. Decompress and extract the data files and the MasterDD file in the same directory.
After uncompressing the files there will be many files in the directory. These files are discussed in detail in the complete SDTS Transfer Description. For a summary, you can download the SDTS Overview document (extracted and summarized from the Transfer Description and other USGS documents) at http://www.fws.gov/data/gisconv/sdtssum.html .
Converting the Data
The aml sdts2cov.aml downloaded above utilizes the sdtsimport command within Arc/Info to convert the SDTS data to an Arc/Info coverage. It also creates all the links between the attribute tables to enable you to identify the features on the coverage. The readme file contains step by step directions as well as contact information if you have further questions. This aml creates double precision data (assuming the original sdts data was double precision), something the sdtsimport command does not do automatically either.
The only type of data that did not completely convert using this aml was the hypsography data. It was necessary to manually add links between the polygon attribute files to identify the polygon elevations; if the polygon coverage was hypso, then the attribute files hypso.ajoin and hypso.ahpt were linked in that order on common fields to the main hypso attribute table in ArcView. See the notes under the SDTS to Shapefile section on hypsography as well for other tips.
Summary of Steps
1- Download data and executables - make sure to get the master data dictionary too
2- Set up directories and subdirectores, placing the compressed files in the correct areas
3- Extract the files (uncompress)
4- Run the aml to convert the files - one for each type of data such as hydrology, roads,
etc.
For additional information regarding this Web page, contact Deb Southworth Green , in the Division of Information Technology Management, at Deb_Green@fws.gov
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Keywords=GIS, data, SDTS, conversion
Last Modified January 04, 2001 07:30 AM