TransDem Trainz question

[Approach_Medium]

Hi;
Can anyone tell me what the limit is on how much DEM I can load at once into TransDem Trainz ver 2.1.3.1?
I am creating DEMs from the USGS Seamless Server at 1/3arc.

Sometimes, when I continue adding DEMs to an existing large area, I get an error (not sure what it says), and operation cannot continue.
It appears that either the program has an upper limit on the size of the working DEM, or my system has a limitation on memory.

My system is Windows 7 Ultimate 32bit
3Gigs DDR2 system memory
NVidia GeForce 9800 GTX+ 512MB
Lots of HDD space, so I am sure it's not that, unless I need to enlarge my pagefile. Virtual memory is now 3072MB.

I am currently creating a route that includes a lot of eastern PA, but I am limiting the DEMs I create to 2 Trainz baseboard tiles on either side of the route, using the rectangular masks, then downloading DEM areas that are within each box.

Thanks for your help

FW

 

[geophil]

Frank,

merging DEMs, particularly at high resolution, is a memory exhausting operation, as a lot of intermediate space is required. 2.1.3.* has already been tuned for maximum efficiency, e.g. the undo stack will be cleared prematurely.

2GB virtual process memory is the limit on a standard 32bit system. You can tweak Windows to allow 3GB and TransDEM will make use of it. See the TransDEM main manual for details.

For even bigger projects you should split your route into smaller modules and merge the modules in Surveyor. Seamlessly.

 

[Approach_Medium]

Thanks Rolland;
Do you know if Trainz (TS12) will also use the 3GB VA?

Thanks

Frank

 

[Laddie]

I had DEMs for the entire UK merged earlier today.

The problem I had was getting satellite images from newcastle to york at a resolution of 1024. My computer wasnt having problems; it appeared that TransDEM was sort of forgetting where to go lol as the progress bar would go from 25% to 100% just north of York.

I think the number of DEMs that can be loaded at on e is down to how powerful your computer is.

 

[geophil]

Do you know if Trainz (TS12) will also use the 3GB VA?

I have no idea. But the Trainz runtime - Surveyor and Driver - will take advantage of the baseboard structure of the .gnd file. The file format allows to selectively read individual baseboards and only read as many as currently needed. TransDEM cannot do this because there is no such tile structure in DEMs or raster maps (not even in Map Tiles, different coordinate system there). This means TransDEM has to load the whole lot.

 

[Approach_Medium]

I have been minimizing the area of DEM I need to use by drawing the polylines for the track first, after loading the raster files, using the rectangular masks. Before this, I was guestimating when selecting DEM area from the Seamless Server, which usually resulted in grabbing way more DEM than I needed.

It kind of disappoints me that Windows 7 needs to be told that I want to use 3GB of virtual memory. I thought by now Microsoft would be smart enough to code it so that it would just use what you've got!

FW

 

[JCitron]

I have been minimizing the area of DEM I need to use by drawing the polylines for the track first, after loading the raster files, using the rectangular masks. Before this, I was guestimating when selecting DEM area from the Seamless Server, which usually resulted in grabbing way more DEM than I needed.

It kind of disappoints me that Windows 7 needs to be told that I want to use 3GB of virtual memory. I thought by now Microsoft would be smart enough to code it so that it would just use what you've got!

FW

This is because of the 32-bit memory limit of 4GB (well it rounds down to 3GB after removing memory pointer areas, etc.). Windows sees what's ever there, and uses it accordingly. Allowing the full use of all the RAM requires a special switch, which I can't remember offhand because I only used it once. There's an interesting article about this up on Technet that I read recently. www.technet.com

This thread also answered a few questions about my issues I've had with TransDem. I too was grabbing huge chunks of land area instead of focusing on a smaller region, and had similar failures. Now this was happening with 64-bit Windows 7 and 8GB of RAM.

John

 

[Approach_Medium]

This is because of the 32-bit memory limit of 4GB (well it rounds down to 3GB after removing memory pointer areas, etc.). Windows sees what's ever there, and uses it accordingly. Allowing the full use of all the RAM requires a special switch, which I can't remember offhand because I only used it once. There's an interesting article about this up on Technet that I read recently. www.technet.com

This thread also answered a few questions about my issues I've had with TransDem. I too was grabbing huge chunks of land area instead of focusing on a smaller region, and had similar failures. Now this was happening with 64-bit Windows 7 and 8GB of RAM.

John

I've got only 3GB RAM, so I guess Windows is using all of it. The switch I am using now is for virtual memory. I think it's a 4GB max for 32 bit.

When you use rectangular masks to select area to grab DEM, make sure you have the "show baseboard grid" turned on so that you can use it to set your bounds. I normally keep the default 2 baseboard grid tiles when generating a TS route from Transdem.

FW

 

[JCitron]

FW,

The 2-grid limit may seem small, but I think that makes things a lot easier to handle when building a route because you can pull in bits and pieces, line it up and then continue. At the moment I'm working with eastern New England, although not very high, it does have a lot of rolling hills that are difficult to do using the other Surveyor methods.

John