How to use USGS DLG vector data

[geophil]

DLG is a large scale US vector map, digitized from the USGS 1:24,000 topo map series. DLG stands for Digital Line Graph.

One of its distribution formats is SDTS which TransDEM cannot read directly. However, after conversion to .dxf, the data can be used with TransDEM.

The procedure is somewhat complex but should yield proper results, eventually.


How to obtain the data

1. DLG in SDTS format is available from this USGS site: http://edc2.usgs.gov/geodata/index.php. Click on "1:24,000 Scale Digital Line Graphs (DLG) SDTS Format Only" to open this area.
   
   Data is structured by state and by 7.5' quadrangle.
2. Click on "State" for the list of states, then on the state you want. e.g. Colorado. You will see the list of quads, ordered by quad name.
3. To identify the names of the quads you need I recommend to use a map finder like this one: http://www.usgsquads.com/index.php/map- ... /mapfinder.
4. Set to "1:24,000 Topographic Quad Index" and select the state, Colorado again. Zoom in or select city. Let's find "Golden, Co". Zoom in until you spot the Rio Grande main line up to Moffat Tunnel. Follow route 93 north then west on route 72. Here we are. We need 4 quads for this bit. Clicking on the "i" icons reveals: Eldorado Springs, Louisville, Ralston Buttes and Golden.
5. Back to the Eros Data Server, the USGS site. Let's start with "Golden". The vector layer is next. We will concentrate on railroads, to be found under "transportation". The railroad files are those with with "RR" in the name. you often find more than one. With a bit of luck, the one with the highest number is UTM/NAD83, the easiest to deal with for later processing in TransDEM. In this case ("Golden" quad), the file is "1531411.RR.sdts.tar.gz". Download to a suitable folder.
6. Repeat for the other quads.

How to convert the data

1. Unzip/untar all downloaded files to their respective directories. Each directory will have a number of ddf files with cryptic names. ddf is a file format for SDTS.
2. Next we we need a converter. I will be using sdts2dxf which is a console program. You can download it here: http://software.geocomm.com/translators/sdts/ (There are other places, too).
3. The easiest way to proceed is to copy sdts2dxf.exe into each of the unpacked sdts directories, the ones with the ddf files.
4. Open a console window for one the directories, let's start with Golden (1531411.RR.sdts).
5. Start sdts2dxf.exe
6. The first prompt will be "Enter base SDTS file name:" Reply with the first four characters of the ddf file names, "RR01" in this case.
7. Next prompt is "Enter the 2 digits in position 7 & 8 of input filename". Answer it's "01" in this case.
8. The third and last prompt will be "Enter base output file name (exclude any extension):" Enter a name. I suggest to use the name of the quad, i.e. "Golden" (w/o quotes).
9. sdts2dxf will list some information and possible display a warning, but it should produce "Golden.dxf".
   

   Code: Select all

   Golden
   Title:                 GOLDEN, CO / RAILROADS
   Data structure:         DLG-3
   Map Date:              1997
   Data set creation date: 20000906
   Scale:                     24000
   
   CAN'T OPEN FILE rr01ne01.ddf, continuing......

10. Repeat for the the other quads.

How to process the data in TransDEM

1. Prepare TransDEM for using vector data by either loading a DEM or a georeferenced raster map of the area with the downloaded DLG quads. I recommend a map, one that shows the railroads, with a scale of 1:50000 or better.
2. Open the first .dxf file, the one for Golden. Set the "Open Route" input data type to .dxf. Locate and open the file. Reply "Yes" to the popup message, where TransDEM offers to remove any boundaries.
   
   [Note: (Fixed in TransDEM 2.1.2) TransDEM 2.1.1 may crash here as I found out today. Apparently this is an error almost 10 years old, from a library written before I started with TransDEM. Will be fixed shortly. If you encounter this problem, leave the boundaries in for the moment.]
   
   The vectors should appear on top of the DEM or the raster map.
3. Verify the coordinates. Compare with the map. If the DLG data has a different geodetic datum, i.e UTM/NAD27, the vectors will not line up correctly with the map.
4. Repeat for the other dxf files.
5. Once all files are loaded, save the whole bunch by choosing "Save route as..." Use the default .str format an accept the default UTM settings for this file.

[PDX-Mike]

Apparently this data is no longer available in SDTS format (*.ddf file extension).

The link in the original post is also dead (404 file not found). I did some hunting around and although I can find DLG large scale files, they are in a *.do file format??

[geophil]

Thanks for this information. I have done a bit of research myself now. It's not as bad as it seems, remedy is on its way: An alternative download address. (I will update the original tutorial later.)

The new address is USGS Earth Explorer, as pointed to here:
http://eros.usgs.gov/#/Find_Data/Produc ... lable/DLGs

You need to register to be able to download.

All in all it looks like a different user interface to the same data.

[PDX-Mike]

Tried that site and registered. Downloaded a file for my local area to see what it was like.

Unfortunately, as I mentioned above, the files they claim are in SDTS format are in native or optional format with only one file in the archive and it is a *.DO format. Appears to be text.

Is this format something that TransDem can import?

[geophil]

Unfortunately, as I mentioned above, the files they claim are in SDTS format are in native or optional format with only one file in the archive and it is a *.DO format. Appears to be text.

Here is what I did. Same example as in the first posting, for "Golden, CO".

On the NewEarthExplorer site:

1. Enter Search Criteria
   In the [Address/Place] field enter "Golden, CO".
   Click on [Data Sets]
2. Select Your Data Set(s)
   Select "Digital Line Graphs" | "DLG Large Scale"
   Click on [Additional Criteria]
3. Additional Criteria (Optional)
   Data Set : DLG Large Scale
   Scale : 1:24,000
   Product Group : 7.5-MIN DLG Trans
   Status Type : Recommended Version
   State : COLORADO (for this example)
   Click on [Results]
4. Search Results
   For each result shown check the meta data (2nd icon). "Overlay" must read "RR".
   (For "Golden, CO" this is Entity ID: DL017616TR177690-1531411)
   Make sure that you are logged in, and click on Download(3rd icon)
   You will get "1531411.RR.sdts.tar.gz", the very same package as with the old site. Unpacked it has all the .ddf files needed for further processing.

[PDX-Mike]

I tried your example, and everything works fine. Apparently the problem is USGS only has limited SDTS formatted coverage. I found that it seems to be very hit and miss in my home state and in southern Washington state. There seems to be full coverage in native format, but not all areas have the SDTS format. I spot checked several places in Oregon and found that even following a rail line in the "earth explorer" window, I could find SDTS format only about half the time. The quick test is that if you only see 3 files pop up in the results, there is no SDTS format for that quad.

I send USGS a message commenting on the lack of coverage and the fact that it is a bit of a pain to have to open the metadata to figure out what format the files are in.

If you open the metadata, and look at the data format type if it is a 3 then it is SDTS, otherwise it is native.

edit, just got a reply to my message, saying that someone will respond in a day... LOL we'll see.

Also been playing around with one of the DLG files I did find, you might add to the tutorial that if the coordinates don't line up, you can close the route file, look at the metadata and see what was used, and set that in view/national coordinate system, then open the file again. In my case the DLG file I downloaded was UTM/NAD27.

Even better might be to look at the metadata and jot down the coordinate system used while you're downloading the files...

[n2airb]

Geophil, Hi my name is Shawn and I am new to Transdem on your " How to use USGS DLG vector data tutorial" you had a link for sdts2dxf any converters that work with windows 7 64 bit? your link will not work with win 7. 2nd question which site do you use for downloadable dems for Transdem? Have a good day Shawn.

[geophil]

you had a link for sdts2dxf any converters that work with windows 7 64 bit?

I haven't tested it on an x64 system it but to me sdts2dxf.exe appears to be an ordinary Win32 console application without any specific requirements.

2nd question which site do you use for downloadable dems for Transdem?

For a US route I would recommend USGS NED DEMs, available on Seamless Server. You will find a short introduction in the TransDEM main manual. A much more detailed tutorial can be downloaded here in the forum.

[Redford1998]

Hello there, is there anyway I can use the data even though its an opt file? Is there any kind of free file converter I can use?

[geophil]

I'm afraid, opt as a vector data format is unknown to me. I'm not sure (and my intenet connection is too limited at the moment to verify) but can't we obtain vector data in shape format via the National Map Viewer?