In this example we import a DDF, SDTS file containing vector data showing roads in the Palo Alto, California, region. We use Selection and the Select pane to eliminate point and area objects, leaving only line objects, and then we use Style to provide a more understandable display. See also the companion Example: Import DDF SDTS DEM Raster File topic.
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.
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 ...CATD.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.
We can double-click the drawing to view it. For a more interesting display, we first create a map using a Bing streets image server as a base layer, and then we drag and drop the TR01 01 Drawing into the map.
The drawing shows a dense collection of objects in default gray formatting color, correctly georegistered where Palo Alto should be on the San Francisco peninsula, exactly placed between Alice's Restaurant near Sky Londa in the lower left and the Palo Alto airport at mid-right. The Googleplex is just out of sight to the right.
Vector drawings imported from DDF will often contain a confusing mix of points, lines and areas. The "roads" drawing above, for example, includes not only lines showing roads but also area objects that cover the regions between the roads and also points at the centers of such areas and at the beginning and ends of lines.
If we like, eliminating everything but the lines is easy using Selection. With the focus on the drawing tab in the map, we use the Select pane.
In the Select pane we choose the Lines template.
Manifold will immediately preview in blue preview color the lines that would be selected. Back in the Select pane we press the Replace Selection button.
That selects all of the line objects in the drawing. We then press Ctrl-I to invert the selection.
Inverting the selection de-selects all lines and selects all area and point objects. We can now press Delete.
Deleting all of the selected area and point objects leaves only the road lines, which appear overlaid on the Bing street map layer that is now visible through the transparent regions between road lines.
We can Style the road lines to change their appearance, and then use them in other settings. For example, in the illustration above we have changed the color of the road lines to orange-yellow and have added a Bing satellite imageserver layer.
The image seen above is the same map published in larger size on the Data Sources page on the Manifold website. In the larger image the horizontal white line at the middle left of the image is the Stanford Linear Accelerator.
DLG, USGS .DLG, .DO, .OPT
Example: Spectacular Images and Data from Web Servers
Example: An Imageserver Tutorial
Example: Import DDF SDTS DEM Raster File