TransDEM Forum

I am working on a USA route and ran into a problem with getting raster maps. It seems as I'm working my way NNW I seem to have crossed a line as I am downloading the raster maps along the route they just appear as large white boxes where the map should be. What am I doing wrong and is there a way to take a screen shot to better show the problem?


Dave

It looks like you are crossing a UTM zone boundary. TransDEM can deal with this.

Have a look at this posting: http://forum.transdem.de/viewtopic.php?p=285#p285

I tried the Transform UTM Zone as per the post but each time I try TransDEM crashes What should I do now?

Could you be more specific? Which particular function causes the problem? Is it a fatal crash (return to desktop) or an error message pop-up? And which version of TransDEM?

When I try to add 2 DEM's together from zone 17 and 16 I see parts of the DEM's that do not connect. I then push the Transform UTM Zone button and get the conformation message and press OK. The program starts to work for about 10 seconds then crashes to the desktop.

There could be two independent issues here.

What do you mean by "do not connect"? To be able to see both DEMs in the same view, even with a gap between them, these DEMs have already been merged (menu command "Add DEM"). And if the second DEM had been in a different zone, zone transformation would have taken place, automatically.

If a gap remains, you will have to fill it in, by acquiring additional DEM data for it.

Which version of TransDEM (Menu Help | About)?

TransDEM may exhaust memory when processing large DEMs, particularly if this involves UTM zone transformation and/or merging. I fixed a problem with an untreated memory allocation error in one the more recent releases (within the 2, 3 or 4GB limitation of every 32bit process).


For the general workflow, remember that the first DEM opened determines the UTM zone. This should be the one which covers the bigger part of the route.

I'm sorry, I meant to say there are gaps and white "seams" between the raster maps around area where the zones meet. Also I can only see one zone of the raster maps. When I switch zones the other side of the raster maps disappear. Is it possible to have both zones of raster maps visible and importable into Trainz?

Dave

Sure. You have to acquire the WMS raster maps from their native zone. This means you need two separate sets of map clippings, one from the primary UTM zone (majority of track miles), one from the secondary zone (minor part).

Transforming the DEM is the correct way to switch the UTM zone to the adjacent one. This is a temporary switch. If you run out of memory (again my question here: which version of TransDEM?), you can reduce DEM raster width for this purpose.

BTW, any vector data will be transformed as well. Due to transformation your polyline path for acquiring the map images will still be valid in the other zone.

Once your have the two sets, load the original DEM again and load both sets of maps. The one from the other zone will be transformed.

You will get some overlapping with white margins at the very edge between the two zones. To get rid of the overlap, use the "Transparent Margins" function.



I should rewrite the tutorial for this. It already existed, on the UKTrainz forum, but disappeared with other valuable information when that forum collapsed.

I would love to see this tutorial on crossing zones! My route seems to be crossing back and forth between zone 16 and zone 17. Oh I upgraded to the latest version of TransDEM. I am trying the map switching now and keeping my fingers crossed I can get it to work

Good news it worked!

Dave

I have finally rewritten it and posted it here.