Spatial Data Transfer Standard (SDTS) format was popular for many years as the primary GIS data interchange standard for the U.S. federal government. Most USGS vector drawings (DLGs) and raster images/surfaces (DEMs) were converted into and published using SDTS format. In both cases the three-letter DDF extension is used for file names that contain SDTS data.
Although the enthusiasm for and use of SDTS has waned in recent years, a vast amount of data has been published in SDTS format and continues to be available for free download from various archives.
The Manifold DDF / SDTS dataport will automatically detect if DDF files contain vector or raster data and will automatically import that data correctly as drawings or images. DDF files specify the coordinate system used by the data they contain so DDF data imported into Manifold will automatically have the correct projection assigned.
SDTS format allows objects such as lines to be defined not just by X,Y coordinates but also by Z coordinates at each coordinate location that defines the line. If Z data exists in the data set, checking the Import Z box causes an additional drawing to be created filled with points, each of which has a Z coordinate taken from the accessory Z values in the coordinate sequences that define lines or other objects.
Importing an SDTS file can create many files: drawings, comments and possibly several tables can be created. To keep the project organized, create a folder into which each SDTS data set can be imported.
SDTS format normally includes a large number of files organized within a folder One of the files often will be a catalog file that ends in "…CATD.DDF". For example, in the illustration below of a folder for road files for Palo Alto published by USGS in their 1:24K series there are 23 files.
One of the files (highlighted) is named TR01CATD.DDF. That is the catalog file. To import an SDTS data set, browse to the directory that contains the files and import the ...CATD.DDF file. Manifold will read the catalog and automatically organize the import of all files involved. If there is no file that ends in ...CATD.DDF then usually a good strategy is to choose the largest file in the folder.
To import from DDF, SDTS format:
Choose File-Import from the main menu.
In the Import dialog browse to the folder containing data of interest.
Double-click the file ending in ...DATD.DDF
Tables and drawings and comments will be created.
Clicking on the TR01CATD.DDF file for the file folder shown above will result in the creation of a collection of tables, a drawing that uses one of the tables and comments.
For a step-by-step example of importing and then Styling a vector DDF file, see the Example: Import DDF SDTS DLG Vector File topic. See also the companion Example: Import DDF SDTS DEM Raster File topic.
SDTS format normally includes a large number of files organized within a folder One of the files often will be a catalog file that ends in "…CATD.DDF". For example, in the illustration below of a folder for terrain elevation data for the Alameda quad published by USGS in their 1:24K series there are 19 files.
One of the files (highlighted) is named 1475CATD.DDF. That is the catalog file. To import an SDTS data set, browse to the directory that contains the files and import the ...CATD.DDF file. Manifold will read the catalog and automatically organize the import of all files involved. If there is no file that ends in ...CATD.DDF then usually a good strategy is to choose the largest file in the folder.
To import from DDF, SDTS format:
Choose File-Import from the main menu.
In the Import dialog browse to the folder containing data of interest.
Double-click the file ending in ...DATD.DDF
Tables and drawings and comments will be created.
Clicking on the 1475CATD.DDF file for the file folder shown above will result in the creation of a collection of tables, an image that uses one of the tables and comments.
For a step-by-step example of importing and then Styling a vector DDF file, see the Example: Import DDF SDTS DEM Raster File topic. See also the companion Example: Import DDF SDTS DLG Vector File topic
Wrong projection in Puerto Rico - Some SDTS files published in past years by the US government for regions in Puerto Rico contain an error in the projection they report. The SDTS file information says the contents use the NAD27 datum but in reality the data they contain uses the Puerto Rico datum.
When such drawings are imported and overlaid on similar vintage US government data, for example, TIGER/Line 2000 drawings, they will not align with the other data. This problem has been observed in 1:24K-scale SDTS DLG files as well as 1:24K-scale SDTS DEM files. It may occur in other files for Puerto Rico that are in SDTS format as well.
To fix this problem, after import open the drawing with the wrong datum and launch Repair Initial Coordinate System in the Component tab of the Info pane to specify the correct initial projection for the imported component. to change the datum to the Puerto Rico datum.
Example: Spectacular Images and Data from Web Servers
Example: An Imageserver Tutorial
Example: Import DDF SDTS DEM Raster File
Example: Import DDF SDTS DLG Vector File