Starting a route using Google Earth/maps

Napalm said:

Casper has hit the nail on the head here with regards to using TransDem for European and UK routes, there isn't a great deal of high quality Dems available for the area.

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Unless you are in the Nullarbor there is nothing like flat terrain in the real world. Plane sea-level baseboards are in invention by Trainz and have no prototypical counterpart. We might not have 20m or better DEMs for free outside North America, but we do have SRTM and GDEM. Jerker has said it. In any case some DEM will always make for a more realistic route than no DEM.

There is nothing wrong with a "Basemap" approach, though, as has been mentioned before. It is one one aspect and one of the established techniques of prototypical route building. There are other aspects and there are other approaches. One might even combine some of the established techniques.

mezzoprezzo said:

It’s probably too much to expect to get a perfectly finished result from DEM software. However, could I expect to get as good a result, or better, with TransDem utilising the Japanese data, than the unfinished terracing results shown in this shot?

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Why do you think DEM software cannot achieve better results? If the original DEM does not have terraces, TransDEM created terrain will not have either. Much has been said elsewhere (not Trainz related) about artefacts in ASTER data. ASTER was available before SRTM and the artefacts too. That's why I implemented some specific algorithms to deal with them, quite early in TransDEM development.

I would always compare SRTM with ASTER. SRTM 3 arc sec is not so bad at all. Better than the terrain in your screenshot. There are other options, too. For the European Alps we have ViewfinderPanoramas 1 arc sec and for the UK we have O/S Land-Form Panorama 50 m.

Hi geophil.

Thanks for helping me to understand a bit more about DEM software.

It is very useful because I don’t really know the capability of what’s available in the DEM world, hence the question, and the screenshot of how I am doing it.

What I still find a bit confusing is how well DEM software can contribute to the realistic result which I am trying to achieve. I can see that the initial landscape forming just has to be so much faster.

What is unclear to me is how close to the real landscape the DEM software will create the map.

With my 25ft (7.62m) interval UK OS contour lines (5m on newer maps) I can tweak until I’m happy that it looks like the real part of the world which I am trying to model. The “invisible track” contour lines are there (until I delete them), so I am able to go back to any area to refine the work in progress. Does DEM software give you similar visible reference points in Surveyor? If so, are they linked as contour lines, or disconnected spot references?

The 50 metre DEM option, if I have correctly interpreted what it might mean, sounds as if will not create the modelled terrain as precisely as manually adjusting to the very much more closely spaced DIY 7.62m contour lines. Is that the case?



Cheers
Casper

A DEM is a kind of kind of digital map with a very simple structure. There are many file formats but the basic idea is always the same. The DEM consists of a two-dimensional array of values. Each value gives an elevation (height/altitude). The vertical resolution of this value is usually in meters. The location for each value is determined by its position in the array and the geographic or projection coordinates of one of the corners of the array.

All points in the array are equidistant. The distance or spacing between the points is the horizontal resolution. For projected coordinates like UTM or the British O/S grid the spacing is given in metres. Many DEMs are in a geographic pseudo-projection, called Plate-Carrée, where the spacing is given in angular degrees or parts thereof.

A "50m DEM" is a DEM with a horizontal spacing of 50m. There vertical accuracy for each point in such a raster is normally 1m (+/- some error, depending on the method how it was created).

A "3 arc sec DEM" is a DEM in Plate-Carrée pseudo-projection where the horizontal spacing in metres depends on latitude. For 50° it yields around 60 x 90 m, still sufficient for hilly terrain.

However, these standard DEM will not reveal any railway lines and their earthworks. There will be no cuttings or embankments. This part of terra forming will be left to the civil engineer working with Trainz Surveyor.


Here is an example (often shown before), the northern approach to the Gotthard Pass, near Wassen (the famous horseshoe curves). The DEM is 1 arc sec ViewfinderPanoramas (ca 20 x 30 m).



The track splines originate from a different project, completely unrelated to Trainz. If you happen to have such accurate 3D vector data, TransDEM can even do some grading for you, too.

Normally you would also paint the ground with a map texture, to help you in placing objects in surveyor. This terrain was intentionally left blank in this example to give a clearer impression of the landscape formed.

geophil said:

If you happen to have such accurate 3D vector data, TransDEM can even do some grading for you, too.

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Are there any sources of 3d vector data for US rail available? I havent found any yet...

High geophil.

Thanks for your detailed reply and excellent illustration.

I understand the process much better now.

The end result looks very impressive. The Smooth Spline has cut away the cliff face a bit too far, but I can see that this is the effect of smoothing in Surveyor rather than the performance of the DEM software. I can also see that there is plenty of space between the track and the steeper terrain to hand adjust many of the intersecting grid points to bring the cliff face, or edge, closer to the track without disturbing the horizontal track bed. Something I’m well practised at using my manual method!

I don’t think I’ve got the heart to scrap and restart my current work in progress, but I’m certainly sold on the process for any future prototypical project.

Thanks again.

Cheers
Casper

mrscsi said:

Are there any sources of 3d vector data for US rail available? I havent found any yet...

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Not that I am aware of. I am afraid you have to ask your favorite railroad company.

mezzoprezzo said:

The end result looks very impressive. The Smooth Spline has cut away the cliff face a bit too far, but I can see that this is the effect of smoothing in Surveyor rather than the performance of the DEM software.

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What you see in this example is the pure result of TransDEM terra-forming and grading, no editing in Surveyor yet. TransDEM offers a couple of parameters to optimize this, within the limitations of the Trainz terrain model.

The biggest restriction for grading in Trainz is the inflexible terrain grid. While this has improved somewhat with the 5m raster, it still requires too broad a roadbed.


Keep in mind though, that 3D vector data processing is still mainly theoretical. Few users will have access to it or will have the means to create such data themselves. It needs a CAD-like editor, although it has been said in the past that a certain model railway track building tool was capable of accomplishing this.

Having been route building for years, I glanced over a DEM thread ages ago but didn't give it much thought, not really understanding what it is.

I've read through this thread with interest and now I'm thinking I'm mad to be making routes from scratch flat boards. If you'll excuse my ignorance here, using Geophil's transDEM software, I can get topographical data for anywhere in the world and translate this onto baseboards in Trainz?

If that's the case, I think it's about time I ordered transDEM and saved myself many lost hours on terrain creation?

Thanks and sorry to sound like some dipstick who's just suffered some mad form of epiphany.

PFX.

pfx said:

... If you'll excuse my ignorance here, using Geophil's transDEM software, I can get topographical data for anywhere in the world and translate this onto baseboards in Trainz?

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For most places on the planet, yes. And certainly for Ireland.

geophil said:

For most places on the planet, yes. And certainly for Ireland.

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I was actually thinking of the Scottish Highlands but I figure if it covers Ireland, I should be safe (I'm actually a Scotsman abroad!).

Looks like I could be making use of Paypal over the weekend then. Thanks.

Well, now that I'm the owner of TransDEM, looks like I have a bit of reading ahead of me but I'm looking forward to being able to create some geographically correct routes in future months/years...

Scotland is covered by 1:50000 and 1:25000 O/S topographic maps. Try streetmap.co.uk. Coordinates are a bit tricky. There is a hint in the manual, this may help, too: http://forum.transdem.de/viewtopic.php?p=8&sid=25ed6f890038367505404ff32f8a56f1#p8.

The blue grid lines on the map are the 1000m lines of the O/S grid.

That's most helpful of you. I'll take a look once I've absorbed the documentation.

Thanks.
PFX

Another hint:

Terrestrial 50m DEMs for Britain: O/S Land-Form Panorama: http://forum.transdem.de/viewtopic.php?f=2&t=25&sid=6513344d585b538680b2d014ae031b67 (See also the very last chapter in the manual.)

If encountering any difficulties, feel free to open a thread in the TransDEM support forum.