Use Didger 2 to Combine SDTS TVPs with Hard Copy Data

Save time and money on projects by using Didger 2 with files from the United States Geological Survey (USGS). Free boundary files, hypsography, hydrology, transportation, and vegetation cover maps are available from the USGS for most areas of the United States. Didger 2 quickly and easily imports these files, also known as SDTS Topological Vector Profiles (SDTS TVPs). The following example illustrates how to combine coordinates digitized from a digitizing tablet with SDTS TVPs downloaded from the Internet.

For example, if you have a paper map of Hawaii showing the topographic contour lines and you want to combine it with maps from the USGS showing the roads and streams, start by digitizing the contours from the paper map using a digitizing tablet and Didger 2, following the procedure below.

1. In Didger 2, go to File | New and choose Tablet Digitizing
2. Go through the calibration steps for your tablet, as outlined in Chapter 3 of the Didger 2 User's Guide
3. Use Digitize | Polyline to digitize the contour lines, recording the elevation of the contours as the Primary ID
4. Save your file as a Didger 2 project (.pjt)

Download the SDTS TVPs showing the roads and streams of Hawaii from the USGS by following the links from their main website, http://www.usgs.gov. The files for Hawaii are currently located at http://edcwww.cr.usgs.gov/pub/data/DLG/2M/HI/.

1. Click on HI.trans.sdts.tar.gz (road data) and choose Save File. Save the file to your computer
2. Repeat Step 1 for HI.hydro.sdts.tar.gz (stream data)
3. Open WinZip and disable the TAR file smart CR/LF conversion option in the WinZip Options | Configuration dialog box
4. Unzip the files and extract all of them to a folder
5. The unzipped files are 1:2,000,000 in scale and in SDTSTopological Vector Profile format (DDF)

Open your Didger 2 project containing the digitized contours of Hawaii. Import the DDF containing the road data by using the File | Import Vector command. Check the "Apply Datum Conversion" check box in the Import dialog box and Didger 2 converts the DDF into the projection and datum of the paper map data. Import the DDF containing the streams using the same procedure.

The result is a map showing the contours, roads and streams of Hawaii produced from combined hardcopy data and data downloaded from the USGS. The free USGS files allowed the project to proceed without the need for laborious digitizing. The new import filters in Didger 2 adds tremendous flexibility to the ability to incorporate files from other programs.

The map above is a completed map of Hawaii, showing features such as road, streams, and topographic contours

Back to Newsletter Index