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Enzo1
January 5th, 2016, 04:03 AM
I recently got TransDEM to help me make a DEM for a particular route I've always wanted in Trainz.
I have a large number of resources ready, but I'm lost on the first few steps of getting started. One of them being complete confusion on where to begin on creating a DEM for Trainz.
So, first off, can a DEM be created from raster maps, or does there have to be an actual DEM involved? If a DEM has to be involved, how and where would one go about getting a DEM for a not so huge area? I'm looking for DEM covering the route from outside of Minidoka, ID (close to an area labeled as Wapi, ID) all the way to Shoshone, ID. On all of the DEM's that I have found, they all cover such a large area, and I'm not sure how to go about figuring out what's what on the DEM.
How could one figure out where exactly the rail lines, roads, water, and rivers are on the DEM? How would one figure out where towns are along the line? Is there a way in TransDEM to cut out areas of the DEM that once I figure out I know are not going to be part of the route?


Thanks!

Vern
January 5th, 2016, 07:49 AM
A good idea Chris is to run through some of Roland's tutorials. These will give some idea of the workflow needed.

DEM sources seem to come and go, the most reliable these days being either the NASA SRTM source or my personal choice the Viewfinder site: http://www.viewfinderpanoramas.org/dem3.html

I prefer Viewfinder as the DEM is seamless - i.e. all the holes and missing data have been patched out. There is a useful location map which should help pinpoint the DEM you need (don't forget to increment by 1 for degrees west and degrees south). e.g. the DEM for a route starting at N43.5, W112.5 would actually be N43 W113.

Once you have your DEM loaded and saved, for a quick test I recommend using the built in map tile server process and Open Street Map. You need to zoom the pop up window to the approximate start location of your route, zoomed in so you can see the course taken by the railway. Extract the map working along the DEM as necessary to cover the whole length. Next step is to use the simple route editor to line trace along the railway and save. Return to the map tile and zoom in to give a resolution of around 1:40000 (any closer tends to produce too many map clippings) then select option to tile along the route.

At this stage I normally exit Transdem and and go whatever folder I've saved the clippings to, then open each in turn to increase the contrast and colourisation - otherwise transposed as is into Trainz tends to leave some of the colours washed out. Once this process is done back into Transdem and re-load your saved DEM, route outline and mapping overlay. Into the Trainz route export screen, I don't normally bother with the second or third option or UTM tiles etc. or laying splines. Be sure to select the option which restricts the baseboard extraction to the area around your route vector line or you will potentially end up with a huge ground file. For TS12 and earlier I normally extracted to around 6 or 7 tiles (baseboards) from the vector which gives distant mountains out to around 5km. If it's a large route you might want to take the option of 5m resolution tiles for the route only and 10m in the background otherwise you will again end up with a 500Mb ground file which Surveyor will choke on. For TANE with potentially up to 15km draw distance that policy might have to be re-visited though if it's a fairly flat route you can get away with much less of a distant horizon.

It sounds far more complicated than it is. Once you've used Transdem you feel the raw power and (like me) will end up with loads of base routes created but no time to get any of them to a point near being finished.

Good luck!

JCitron
January 5th, 2016, 10:34 AM
Chris,

This might help:

http://1drv.ms/1JKCOtc

Read through the online guide. Then give it a try. You'll find that there are things you'll never, ever use.

JCitron
January 5th, 2016, 11:03 AM
To add to what Vern says here, besides me reiterating above about reading the tutorials, the NGS supplies the DEMs as 1 arc second slices at a specified resolution. 1/3 meter resolution is the best for the majority of the work, and if you really need a high, high resolution you can use 1/9 m resolution, though these are not always available.

I find the best way to go about this is to download the raster maps first either within TransDEM, which is pretty easy or to use USGS historic Topomaps and convert them in TransDEM.

Once I get the maps I want, I stich them together since georeferenced maps can be butted seamlessly in TransDEM.

With my now saved larger map, I then place this on my DEM, and trim out the rough area in TransDEM to correspond with the mapped area. This gives me a hunk to use and discard the rest.

It's with this chunk that I do my final route trimming and then export to Trainz for further work including trimming up.

With experience, you can do the above in about 15 minutes or less.

John

Vern
January 6th, 2016, 11:00 AM
The USGS also do a selection of historical maps in geopdf format. These take a couple of extra stages to import into Transdem but georeference without having to manually enter co-ordinates at the corners and invaluable for building long closed routes.