Can you use current USGS data for TransDEM for the 'map' ?

[Christopher824]

Can you use current USGS data for TransDEM for the 'map' ?

The USGS has really changed it's website recently, or at least from my prospective. There is no way I can find the simple 'directory' of files, and the site wants to drive me where it wants.

So does anyone know the link to get the data for TransDEM, at least the topo data. I do have a USGS account and can login.

 

[OddRails]

I assume that you understand that TransDEM uses DEM (Digital Elevation Model) files for the terrain and then overlays maps (topo or otherwise) on top of the terrain. It sounds like you've already been using SRTM files for DEMs. So some of what I've written may not be useful. The USGS web pages and links can certainly lead one on a wild goose chase.

For DEMs (terrain files) and GeoPDFs (2D map files) I often use the USGS's The National Map downloader client at:
https://apps.nationalmap.gov/downloader/#/
It takes a while to get used to the interface. The TNM downloader link is useful if you are looking for higher resolution DEMs. SRTM files have a 30 meter resolution and you can get higher resolution DEMs from the link listed.

A few days ago, the above link wasn't working and I did a web search for "SRTM data" to find an immediate source while the USGS site was down. I don't remember which one I used, but I didn't bother with any site that requires registration. I replaced the SRTM files with higher resolution DEMs after the above link was working again.

It is also useful to configure TransDEM's "Map Tile Server" feature found under the Raster Map tab instead of using topo maps for the 2D maps. (See TransDEM's user manual.)

The GeoPDF topo maps sometimes have a small offset which may need additional work to fix. I believe that TransDEM's creator wrote that it expects GeoPDFs to use the NAD 27 format rather than the NAD 84 format that many GeoPDFs actually have. (I may be remembering the wrong numbers.) He recommends using the Map Tile Server feature instead for the 2D and topo maps. The map tiles should not have offsets.

Each TransDEM user seems to favor various sources for the maps depending on either ease of use or desired map detail.

Hope that helps,

 

[JCitron]

TransDEM can convert the GeoPDFs and even rotate them accordingly to fit.

You can still download the .img files as well. They're tucked inside a zip file sometimes, so only extract the .img file and throw the other part away unless you're a data hoarder like me and keep them for just in case.

Here are the steps to convert your GeoPDFs within TransDEM. I put this together in a bigger distilled user-guide ages ago back in 2015.

Startup TransDEM, and choose Raster Map from the menu.
Choose open Raster Map and open up one of your GeoPDFs.

Now this is important:

If these are old maps you can skip this step...

For new maps the open dialog will bring up some a new dialog boxes. Apparently, the new maps have layers. Check only the middle box for Map_Frame and ignore the rest.

Trimming and fixing up for assembly...

The map will load.... Click okay to dismiss the warning about the map "being too big".

Trimming and rotating is done in 3 mouse clicks.

1) Click transparent margins.
2) Click transparent margins again and the outside will turn brownish-beige.
3) Click on Convert to UTM.

The map will flicker and the margins will disappear and the map will rotate.

4) Save the map as a GeoRef. map

5) Repeat for any other PDFs you have downloaded...