TransDEM Forum

Hi All.

Another Newbie with a probably simple problem.

I downloaded the OS Land Form Panorama, and I want to create a route from Crewe to Carlisle but I am totally lost as to determining the right DEM tiles to import, as to which Im just adding tiles in the hope that i find the right ones, but this is time consuming.

Is there anyway of determining the right tile for the right place with the data from Land Form?

And one final question - where do I get the vector data once ive done the DEM importing?

Many Thanks

Andrew H

Duh, did a bit of searching and found the answer to the first question, but in that thread there was still a doubt as to whether the vector files worked. Is that still the case or can we use them?

As ever, much appreciated

Andrew H

Too late.
Prepared an answer already:


Originally posted here: http://forum.transdem.de/viewtopic.php?p=7#p7 (also in the manual):
"Data is packed into tiles of 20 x 20 km and structured by O/S grid squares. To find the grid square, an overview map should be loaded in TransDEM and the coordinate system switched to OSGB36. Grid square codes are shown in the TransDEM status bar, if the View | Show grid square option is activated. The numerical digits in the file name indicate the 20 km tile in square coordinates, the first digit for the easting, the second digit for the northing."

Now, what is an "overview map" in this context? The easiest would be using a Map Tile provider. Once the map tile setup has been imported (TransDEM main manual, tutorial 7, on page 130), these online maps can be used right away.

Example:

Find your area with the TransDEM Map Tile client. Zoom level 12 is recommended. Download a map. 1024 or 1536 pixels in size.



Switch coordinate system to OSGB36. Switch on the grid square option.



Check the status line. Positioning the cursor on Droitwich (in the example) will give something like this:
SO 89600 63400

Grid square SO.
First digit easting: 8
First digit northing: 6
File name SO86.asc

Your directory path will look like this:
\OS Open Data\panorama_gb\DTM\ASCII\data\so\so86.asc



You may need to add more squares.

Open each .asc DEM file individually in TransDEM first and save. Saing will produce .dem format. Then merge the .dem files, using the TransDEM Add DEM function.

These work fine now. See here: How to use OS VectorMap™ District (ESRI® Shape format).

:Ah Ha! Marvellous, it all worked It worked even better when I changed the datum to the correct one...It kept coming up dummy, then when I followed your instructions it all clicked together!

Thank you very much for the help Roland, its a fantastically usefully powerful program

All the best

Andrew

Another question : when its all been exported to Trainz, is there a feature which allows you to make an edge in the terrain elevation for the track to run?

In other words, before its all exported, can the rail vector not position itself on the DEM and when the raster map is imported into the DEM and then its all exported to Trainz, is there any feature which allows you to smooth the track spline before it enters trainz, or is that somthing you have to manually do?

Andrew

G'day AndrewJH,

Technically, Andrew, the answer to your question is outside the purview of this forum, as that which you seek to achieve must be done in Trainz and cannot be accomplished in TransDEM...

..when you export the route to Trainz, TransDEM places the track spline (if you have opted to enable that capability in the export), along the route polyline. It does this by placing a 'spline point' in the Trainz Terrain at each 'point' location along the polyline you have provided as you marked out the route polyline. Each of those spline points are located on the terrain at the height of the terrain at that point, which may (or may not), be the correct height for the prototypical track height at that point. In between these points, the track describes a straight line or curve on a 'straight' gradient, up or down, depending upon the relative heights of the points (thus appearing to go through the terrain where the terrain is higher than the track or to be above the terrain when the terrain is below the height of the track). If the actual track SHOULD be higher or lower relative to any given spline point on the terrain, then you must manually adjust the height of the point up or down at that location, accordingly. When you have down this, you can then use the 'Smooth Track Spline" function to have Trainz automatically adjust the terrain along the length of the chosen section of track, to create embankments and cuttings for you (see the Trainz manual for more details)...

...you can have TransDEM export the polyline for you with the polyline points at the correct prototypical height, if you use a 3D polyline created from a 3D line representing the correct gradient profile of your railway line, which must be created in an external 3d program and imported into TransDEM as a *.dxf file...

Jerker {:)}

Thank you Mr Jerker, it more or less confirmed what I thought

Much appreciated

Andrew

The only other option would be track geometry in 3D vectors. The railways have it, in their digital permanent way database, but inaccessible to us earthlings. With 3D vectors TransDEM would be able to adjust the terrain.