DEM UK Help

[PortLineParker]

Hi all,

I have a problem I'm afraid. I acquired TransDEM today, as I am attempting to model the Purbeck hills around Corfe Castle in Dorset (for those who don't know, I am constructing the Swanage Railway, thread is in freeware announcements). I realise that there is a steep learning curve, but I simply cannot get to grips with it. I have two main problems:
1) Where do I get the geological data
2) How do I import it into TransDEM?

If any sites could be directly referenced with a detailed, really detailed, tutorial that'd be so helpful and much appreciated. I know there are tutorials out there, but the ones I read all apply to US routes. I need to know where to download UK data, how to do it, and how to import it into TransDEM. I can't offer much in return, but for those who want it, a copy of Swanage Railway prior to its release will be available. I realise it's not much, but without the assistance of this wonderful forum it will never see the light of day. Thanks for any and all help in advance.
Many, many thanks,

PortLineParker

 

[clam1952]

Ordnance Survey Open Data http://www.ordnancesurvey.co.uk/business-and-government/products/opendata-products.html

I've dabbled with it in microdem a while back made a test DEM of the Isle of Man can't add anything useful really like the routes with microdem for the UK though.

Actually I've just got Transdem as well, been looking at it tonight and done the tutorials OK.
I downloaded everything from the OS last year, it's all free even though you have to order it. Used to be an apprentice mine surveyor in a previous life for the NCB, so I like anything relating to maps, used to make them both above and underground.
I think Roland has some info in one of his threads on what's actually needed, if I find it before you do I'll let you know!

 

[PortLineParker]

That's great, thanks. But how do I actually download a DEM of Corfe and then import it into TransDEM? Sorry if I sound whiny, just want to get it done

PortLineParker

 

[pfx]

Have you done the tutorials in the manual? If not, DO.

TransDEM is not simply a case of downloading a DEM and chucking it into Trainz and it sounds like this is what you think happens. You're trying to run before you walk here.

There is quite a rigid learning curve involved with making your DEM and you MUST do the tutorials before attempting it. Once you've been through the tutorials and made a simple DEM, transferring what you've learned to create your own DEM will become relatively easy. If you're stuck, get yourself on the TransDEM forum as Roland provides excellent help there.

 

[geophil]

DEM

Best free data: O/S Terrain 50 (replacing Landform Panorama). It's briefly explained last chapter in the TransDEM main manual and in this thread:
http://forum.transdem.de/viewtopic.php?f=8&t=5

You can also use SRTM, of course, as suggested in the the TransDEM Quick Start Guide, but the terrestrial O/S data is better quality - unfortunately a bit more work.

To obtain the right coordinates, start with the map, see below.


Maps

Several options here. Arguably the easiest one for today's railways is the O/S Landranger and Explorer series, available as Map Tiles from MS Bing, under its original name "MS Virtual Earth" in TransDEM, the type is named "Other 1", from the TransDEM Map Tile sample settings. Doing the Map Tile tutorial first is essential, TransDEM main manual.

Go to zoom level 14 for the 1:50,000 series, good for the 10m raster in Trainz, or zoom level 15 for the 1:25,000 series, 5m raster in Trainz:



Alternatively, as seen in the 1950s/60s edition of the 1:25,000 map:



This thread again for more info:
http://forum.transdem.de/viewtopic.php?f=8&t=5


How to find the DEM file(s) you need (also in the manual, in short form there):

Once you have the map in the TransDEM main window, switch to OSGB36 coordinates (View menu), turn on "Show Grid Square" (View Menu). Look at the status line. In my example it reads SY 99878 83328 (You'll probably be familiar with O/S coordinates as you can't really escape them in the UK.)



After you downloaded and unpacked the O/S Terrain 50 data set you'll find all the grid squares in ..\terr50_gagg_gb\data\. Our grid square in SY 99878 83328 is SY, of course. Accordingly we navigate to terr50_gagg_gb\data\sy.

Now we need two digits, one for easting, one for northing, to identify the file. The two digits represent the 10km value. The digits we need are the leading ones in the five digit numerical values in the status line SY 99878 83328. That gives us SY98 and we find sy98_OST50GRID_20130611.zip as our DEM. Unpack. Open SY98.asc in TransDEM. Confirm OSGB36 coordinates and you'll get what I have shown in my screenshot (DEM shading on, intensity and transparency slightly tweaked).

If you need more than one square - quite likely - open each one individually first and save again which produces the same file, converted to UTM and in .dem format. Then, in a second step, open the first of the newly generated .dem files and use "Add DEM" to merge with the other ones. The Add DEM function only understands .dem format and UTM coordinates.

 

[davidbird]

The TransDEM helpfiles and the forum http://forum.transdem.de/viewforum.php?f=1&sid=e6071dc554ee19ce5c3f2a2fd6d4968a.

Have you ordered/downloaded the OS Opendata that clam mentioned?

Do you have topographic maps of the area? Either scanned paper maps or downloaded are suitable.

These are essential pre-requisites before you start using TransDEM.

Any problems with using the program, best to post on the TransDEM forum linked to above, as here help is readily given and we WILL be able to get you going

Edit: 2 more replies as I was typing!