TransDEM Forum

So I am new to TransDEM, but have all ready successfully made one route using it and the Google Earth Images as ground textures tutorial provided by ModelerMJ. But that was a small 6 mile route that easily exported as a a rectangle when I high lighted just the area I wanted to make a route out off.

For my next project though I am doing a much larger route, and thus a much larger DEM. My question is this, is there a way to select only the part of the DEM that I am making to export?

As it is, when I export to a route, all the black areas, and parts of the DEM's I dont want included. Heres what my DEM looks like so far:



I only want to export the colored areas, and not the black zones. Is there a way to remove that? (Note, I have yet to add my GEOrefed Google Earth images as I haven't gotten to that step in my processes yet.)

Any help is appreciated.

Yes. It's called the Route Filter and it's based on vector data. You need the course of your route as a polyline. Then, during export, you tell TransDEM how many baseboards TransDEM shall create on either side of your route.

You will normally create the vector data yourself, by drawing with the built-in Simple Route Editor. For this, you will need a georeferenced map in addition to the DEM and then trace the route on the map.

Thanks, that works!

But next question, when I go to export into Trainz, part of my route is cut off.

Here's my route in TansDEM:



Every thing on the right side of the right most horizontal pink line is left out. Now part of this route is a reuse of my first attempt that building a route trough TransDEM that worked just fine. (Its the branch line in the middle)

Any advice, or what am I doing wrong?

TransDEM writes an info file when exporting to Trainz. It resides in the route export folder, it's plain text and it's named <your route>_TransDEM_info.txt, like this example:


Check "UTM Northeast Corner Easting". Does it go beyond "300000" (the easting value of the second grid line in your screenshot)?

Yes, yes it dose. This is exactly what my file says for UTM Northeast Corner Easting:




It may not be needed, but heres what the rest of the file looks like:

According to this info file, the generated Trainz route extends 4880 m eastward from the second grid line at 300,000, about 3 mi. (UTM coordinates are in metres.) The grid squares on your screenshot are 20 x 20 km. This would fit. Therefore, from the figures, it looks okay. But you say, that's not the case.

There could be problems with memory exhaustion which in rare cases might lead to a premature termination of the export task. Your module, however, does not seem to be overly complex. What DEM resolution are you using? Your overlays appear to be aerial images. How many are there? What are the pixel dimensions?

(As a side note: Aerial images don't work well as a Trainz ground texture, not even with the 5m terrain grid. You'd better go for the 1:24k topo map, which you can acquire via WMS, USGS National Map.)

I followed steamboateng's tutorial on how to make a DEM and used 1/3arc data. I then used ModelerMJ's tutorial on how to use Google Earth images as ground textures, hence why they are there. I used 31 images over laid on the route.


It appears as the TransDEM is cutting off my route cleanly at that line.

If there were memory issues I would expect TransDEM to pop up an error message, however, there are a few exceptions, where TransDEM can't detect this early enough.

1/3 arc sec for your project area of about 100 x 25 km at 10m resolution would require approximately 100 MB, if my calculation is correct. During export TransDEM TransDEM will allocate much more memory temporarily. Nonetheless, I wouldn't expect it to exceed available virtual memory here.

31 images, in compressed state, and depending on pixel dimensions, should also fit.

Now, to make sure, it's not a memory exhaustion problem, try to export only a smaller part of the route, using a rectangular mask. If that succeeds, try with another bigger part.

I tried that and I am able to export any part of the route that I select in its whole. But if I try to export the whole route, weather marked with the rectangular mask or not it stops right at the pink line. I can export the whole lower half of the DEM with out losing any thing.

If its a computer memory issue, I have 6 gigs of ram. Unless TransDEM is having the issue.


I am still trying different things. So far I can export up to half of the route with out problems.

Well, you should be able to seamlessly merge modules in Trainz Surveyor later. You may be aware of the Trainz baseboards created by TransDEM being bound to UTM coordinates. The info file, already dealt with above, and the top area of the TransDEM export dialog with its export region controls should assist you in finding the proper module border.