How accurate can you make TransDEM routes?

[nikkigirl1]

DEM won't do track embankments or rail beds it only builds ground textures and gives you a real landscape.

That is what I want TransDEM to do, build a landscape that includes a 4 mile long, 100-foot tall mountain along with various cuts and fills that are massive parts of landscape for nearly 30 miles. Its not like I want a roadbed that sits ten feet above the ground it is above, I am wondering why a, for lack of a better term, large land masses that contrast greatly from their surrounding landscape do not appear on digital elevation models. If it wasn't a landmark, I wouldn't bother with it, but this is something that the area I live in used to be known for. If worse comes to worst, I have a route where I handmade the whole Cutoff, albeit not well yet.

 

[Seane2c]

I think you need to do modification no matter what. The way I look at it is this saved me a hell of a lot more time than building it from a flat ground alone. Not to mention the ability to plot the mains or other stuff if you want.

The challenge I'm at now is the grades. I use 2 methods and not everyone has access to the 1. 1)Visual observation though this can be supported by Googlemobile images in some areas, it doesn't get to everything and the zoom is not as good as most cameras. 2)quick drive and look for a pattern. I'm not sure the best way to accomplish this yet.

It's kind of like reading a stock market graph where you're looking for trend. So a stock has it's ups and downs but it's the trend line that often represents the normal (or the moving average). Usually I find the track will change grade for access to rivers or grade crossings. Still it's hit and miss, and a bit of guessing.

One lesson I seen and I follow, be careful when filling in the DEM. I've actually taken tracks off the surface (safer) or let them stay buried in the ground until I'm as sure as I'm going to get. There are a few places where I'll have to make some cuts and build some roadbed up. But if I can't see the difference very few if any will.

Always looking for better strategies at accomplishing this though.

Thanks

Sean

 

[geophil]

I have used a different DEM source along with messing with the grid width when creating a new DEM, I set it around 30m grid width I think, I don't know if it did anything anyway but if anything it just added a small hill where the Pequest Fill is. Should I lower that value down to 5m as well?

Try the original USGS 1/3 arc sec from TNM. TransDEM will convert it to a 10m grid. And this fill is quite a prominent feature indeed.

With an Open Topo Map overlay:

Edit: Yes, I would go for the 5m grid in Trainz. While it won't bring out more detail from the 1/3 arc sec DEM, it will allow you finer grade post-processing in Surveyor.

 

[nikkigirl1]

Edit: Yes, I would go for the 5m grid in Trainz. While it won't bring out more detail from the 1/3 arc sec DEM, it will allow you finer grade post-processing in Surveyor.

So when pressing "new DEM" put the grid width to 5m when I get the prompt? I know to set it when exporting, but that initial prompt was confusing. And one time when I tried that, TransDEM ran out of memoryb when I tried exporting even the smallest portion of the route, I probably did something wrong there. But seeing as how the entire route with cuts and fills shows nice in your screenshots, do you think that they would at least be identifiable upon export besides just the blue trackbed line? And along with that, I know TNM doesn't really make the downloading of the DEM data easy when you're in the national map viewer, so how would I go about getting them once I'm on the link that you put in your post?

 

[geophil]

So when pressing "new DEM" put the grid width to 5m when I get the prompt? I know to set it when exporting, but that initial prompt was confusing.

It's set during "Export to Trainz", in the lower left corner. "Route only" might suffice, as long as you have the vector lines of your route loaded. It will affect all baseboards touched by the vectors, the others will be left at 10m.

do you think that they would at least be identifiable upon export besides just the blue trackbed line?

Yes, it should be more than just noticeable. The fill is more than 30m wide in the DEM.

And along with that, I know TNM doesn't really make the downloading of the DEM data easy when you're in the national map viewer, so how would I go about getting them once I'm on the link that you put in your post?

Oh, TNM usability has improved significantly.

• In TNM, zoom the map to your area.
• On the left panel, select "Elevation Products (3DEP)".
• Select "1/3 arc sec DEM".
• Click "Find Products".
• It should at least show "USGS 13 arc-second n41w075 1 x 1 degree". You can check with "Footprint".
• Download all DEMs relevant, you may also want n42w075. File format these days is GeoTIFF, in a variant that TransDEM should be able to decipher.
• Open the DEMs in TransDEM one by one, accept the preset 10m grid (no need to use 5m here, since we do not have any 1/9 arc sec DEMs). Save each DEM (converting to .dem format).
• Merge all DEMs in TransDEM, using the "Add DEM" function.
• Load your raster maps.
• Load your vector data.
• Export to Trainz, selecting 5m grid, "Route only" or "All".

 

[Seane2c]

I hate to start again but I think I want to at least give it a try in hopes that my grades may improve, as well at the UTM overlays with DEM.

I'll let you know how I make out.

Thanks

Sean

 

[nikkigirl1]

I hate to start again but I think I want to at least give it a try in hopes that my grades may improve, as well at the UTM overlays with DEM.

I'll let you know how I make out.

Thanks

Sean

Use those steps. I now have an almost completely accurate route straight out of TransDEM. Thanks to geophil for teaching me how to use TD better or I would have probably given up on this route