GeoPhil....Could use some help with TansDEM 2.1

[Bananimal]

K, where to start. I'm trying to build a route that spans from New Orleans to Baton Rouge, Louisiana. I have gone to the USGS server and downloaded 22 x 24k chunks of 1/9th Arc DEMs. Also, I pulled 1.0 mpp ortho and route shape files from the same 24k chunks. These chunks are seamless and do not span across a UTM zone. All are UTM zone 15. So, everything is neatly packaged in my route folder for processing in TransDEM right? You would think so.

Anyway, for the life of me I cannot get a good export to Trainz on these 24k chunks. Either TransDEM comes back and tells me "could not find a baseboard for UTM tile xxxxxx at xxxxxx" even though I'm looking at the 1000m x 1000m ortho that covers the entire tile or TransDEM for whatever reason refuses to align adjacent tiles up in Trainz. TransDEM sometimes creates full tiles in areas that I have masked halfway not expecting it to pull the tile because the instructions state TranDEM will not pull partial tiles. Well, installed on my PC sometimes is does and sometimes not.

I just did a test where I masked 4 tiles from a DEM with an ortho overlay and created a route. Then I created another route using the adjacent 4 DEM/ortho tiles along the route. I wanted to see if TransDEM woul properly line these tiles up in Trainz for a clean merge. This is off the SAME 24k DEM/ortho chunk from the USGS. The first attempt threw an error stating that "Tiles x and x do not exist an will be skipped." While processing the second set of four 1000m x 1000m tiles, one tile was not found. And, once again, the two 4 baseboard routes REFUSE to line up properly in Trainz.

I an extremely frustrated with this as I have tried all kinds of different ways to be able to start building my route in Trainz. 3 weeks 8 plus hours a day have been spent. While I am not a software engineer I am a software Q/A analyst with 20 years experience in the industry. No matter what I do, I cannot merge the tiles in Trainz as they are off set. How can this be when masking two adjacent areas off the same DEM/Ortho chunk of USGS data? There is a bug or something here. Not sure if it'll help but I am running Vista x64.

Any help would be greatly appreciated. I have scoured the manual over and over and have follwed the instructions to a T. I have already purchased payware assets to use in this route but I am dead in the water if I have to fight TransDEM to make it happen. As of right now, the only option I have is to merge all 22 24k USGS chunks in TransDEM and export as a single route. I don't have 24GB of RAM to make that happen though so I MUST break the route up into smaller pieces for exporting into Trainz.

I was also wondering if it would be possile to include a "snap to grid" masking option in TransDEM? This would give the user much needed control over exactly which tiles to export into a route.

 

[Sek_Hakuna]

You will get a quick reply from the author of Transdem at http://forum.uktrainz.co.uk/viewforum.php?f=131

I use Transdem myself and have no problems creating routes with the raster maps or maptile servers. I use the tutorials supplied with the program.

Randy

 

[gawpo50]

TransDEM

Hi

I had a similar problem when I first used TransDEM, had me tearing what little hair I had left out. Here is the solution I use and have got it working successfully for USA maps. On a large route, break up your exports into smaller chunks that you computer can handle. When you open the export window, look in the top right hand corner of this window where it says 'Baseboard UTM Grid Offset' and change the 'y' setting field to -10m. If I remember correctly, the first chunk I exported was with default settings and for every chunk exported after that, I used the above setting. Works fine for me and can merge at will in TS2010. Hope this little bit gets you around your problem.

Regards
Peter

 

[Bananimal]

Thanks for the reply. I'll try that. It's somewhat interesting that this seems to be a problem in the region I'm trying to model. I bought the DEM utility for Railworks and was unable to start a route for this same area because there is a glitch in Railworks that did not recognize the coordinates of this area.

Something that is not clear in the TransDEM instructions is the issue of half/partial tiles at the boudries of each 24k USGS chunk. Will I need to merge two georeferenced raster maps and DEM files in order to get the UTM tiles I need on the edge of each chunk that are not complete? I have been having problems with this as well.

 

[Vern]

Just a suggestion - have you tried seeing what happens if you used the "pre-packaged" SRTM hgt data from the NASA server? The 2.1 version is now quite high resolution, 20m or 30m standard. These can be merged to cover your area of interest and saved under a custom name. The resolution should be more than adequate to give accurate terrain for a train sim route.

After drawing the route on the map overlay, you are remembering to correctly "mask" the extraction so Transdem only generates the baseboards/tiles required to a given width either side of the route and not trying to extract the whole DEM'ed area?

Only other suggestion is, after processing the DEM is to exit and restart Transdem as on a couple of occasions the programme has locked up after working with particulaly large maps and/or WMS downloads.

 

[wreeder]

Something that is not clear in the TransDEM instructions is the issue of half/partial tiles at the boudries of each 24k USGS chunk. Will I need to merge two georeferenced raster maps and DEM files in order to get the UTM tiles I need on the edge of each chunk that are not complete? I have been having problems with this as well.

Have a look at either the TransDEM 1.2 or 1.3 thread in the Payware forum. Geophil gave me complete directions on how to do this. I ran into it while doing a DEM based route of the RGS.

William