TransDEM Forum

New passerby. I've been working (10 years) on a Mad Plan to create 3D models from DEMs and DLGs (or other vector files) with the 2D vector features (roads, RRs, streams, etc.) "cut" into the DEM.

As you know, Digital Elevation Maps (DEMs) don't have the elevations of the roads, etc., except for the biggest "roadcuts," so I've off and on tried to come up with a way to "cut" the roads into the surface or "build them up" onto it.

Q. Is it possible to load a 2D vector file of roads and a 3D raster of a co-located DEM and output a 3D model of the tracks of individual roads?
(That is either a model containing just the "3D curves" of roads winding and climbing in 3-space or an entire 3D model with roads "affixed"
to the surface.)

It was while trolling the web for "fit road to DEM" that I stumbled on TransDEM, but I haven't found a positive answer.

Thank you for your patience.

G. Roost

The answer would be No, not in the way you are expecting it to work.

What TransDEM can do, in conjunction with the Trainz target landscape, is to cut 3D (!) vector data into the terrain. The DEM itself will not be affected.

To illustrate the process: TransDEM takes the DEM source of any resolution and re-samples it to a 10 or 5m grid which will be encoded as a Trainz "ground" file, representing the terrain for the Trainz railway simulator. TransDEM can then modify this terrain with 3D vector data. The 3rd dimension is important here for proper cuttings and embankments. Parameters determine the threshold for tunnels or bridges.

This screenshot with a Trainz landscape adjusted by 3D railway track geometry is taken from my website:



Note 1: The abandoned project MS Train Simulator 2 claimed to support generic route generation based on freely available DEM and vector data all over the world. We have to assume that such vector data would have been 2D data. Details were not revealed, though.


Note 2: USGS 1/9 arc sec DEMs provide a resolution large enough to model even smaller man-made features:

(Click to enlarge)

Thank you for a quick answer and an insightful example.

I congratulate you for being able to do this!

I have been coding off-and-on for about 10 years trying to make something like what I described. And I must confess I am close. However, I've been close before, but this time, I've been close for 3 years... ;^)

I'm feverishly trying to finish something that I can take into the nursing home with me. So it has to run on an Etch-a-Sketch.
--
G.R.

Hi Roland,

Would you be kind enough to remind me, where in the manual I can find how to fine tune Track vector line in the Trainz export module, to shape threshold for tunnels and bridges as well as for embankments.

I guess track is disconnected between tunnels on your pic, isn't it?

Thierry

Hi Thierry,

you'll find the parameters explained in the TransDEM Trainz Manual, chapter "Menu Item: Export & Create: Track Splines..." starting on page 27. The defaults should give pretty fair results but a tweak here or there may improve them.

Remember that you need proper 3D vector data for this to work. I was using an external tool to obtain this data.

Regarding the tunnels, the track created doesn't care about tunnel portals, it passes right through the mountain.