Hog hight ranges??

[bassist118]

Hi guys,

I've found the dem files for Tibet with view to recreating the Tibetan High Plateau railway. I need something to run those wonderful Chinese locos on. I have sorted the first portion out in nicrodem, got the height range which is 3521m - 5702m.

I've sea level as being -3000m so the height I put into hog was -3000m min and 2702m max. However every time I try to commit the edited mapfile trainz crashes.

Can anyone shed any light onto the problem or is the height range too great for the hog program and I assume Trainz has always had a -3000 to 3000 metre height range since the hog program was written?

Thanks guys

:Y::Y:

Andy

 

[cascaderailroad]

I believe that TRS2006 has a baseboard height range of -6000/+6000

 

[RPearson]

The limit in Trainz is -3000 to 3000m. I think it's been that since at least UTC.

I don't believe HOG has any defined limits for heights. HOG's companion program, PIGLET for making image files from .xyz ascii dems, has a default range of -1000m to 9000m.

Shortline2 has posted on this subject a few times. She found that HOG created maps with heights outside the -3000 to 3000m limits worked in the game but you couldn't make any changes to them. If you edit the map in Surveyor heights outside the limits revert to the limit values.

The height ranges you posted confused me though. If you use -3000m as the reference 0 level and the lowest elevation in the dem is 3521m, your height range input to HOG should be 521m to 2702m. The height range you input should cover only the actual range of heights in the image file. If you specify -3000 to 2702 for the HOG input range you'll get a lot of distortion in the resulting terrain.

Bob Pearson

 

[bassist118]

The limit in Trainz is -3000 to 3000m. I think it's been that since at least UTC.

I don't believe HOG has any defined limits for heights. HOG's companion program, PIGLET for making image files from .xyz ascii dems, has a default range of -1000m to 9000m.

Shortline2 has posted on this subject a few times. She found that HOG created maps with heights outside the -3000 to 3000m limits worked in the game but you couldn't make any changes to them. If you edit the map in Surveyor heights outside the limits revert to the limit values.

The height ranges you posted confused me though. If you use -3000m as the reference 0 level and the lowest elevation in the dem is 3521m, your height range input to HOG should be 521m to 2702m. The height range you input should cover only the actual range of heights in the image file. If you specify -3000 to 2702 for the HOG input range you'll get a lot of distortion in the resulting terrain.

Bob Pearson

Ah right I thought you had to specify base level as sea level not the lowest level on the map.

Edit:
Tried the different height ranges, Trainz still crashing when committing the map. I started a new route, saved it, opened it up in surveyor and edited in windows, then deleted old gnd file and replaced with generated gnd file, then committed at this point trainz crashed, have I done everything right?

Cheers

:Y:

Andy

 

[RPearson]

CM3 crashes when you try to commit the map is that correct?

How big's the .gnd file?

I know HOG runs into memory limits on large gnd files but I don't know if it can make a gnd file large enough to crash CM3. CM3 doesn't appear to check the file itself as I've had it commit invalid gnd files that were pretty large - close to a gig but it crashed on 1 that was 2.7 gigs.

Bob Pearson

 

[Dermmy]

... got the height range which is 3521m - 5702m...

Andy

If you tell HOG the height range is 0 - 2181 you will get the results you are after. The heights will be 'wrong' in an absolute sense, but the relative heights inside the map will be spot-on, and Trainz will accept the height range...

Andy

 

[bassist118]

If you tell HOG the height range is 0 - 2181 you will get the results you are after. The heights will be 'wrong' in an absolute sense, but the relative heights inside the map will be spot-on, and Trainz will accept the height range...

Andy

RPearson - The gnd file is approaching 1 gig I've cut a large portion of the map that's not used, the first time I tried to commit the map into CM3 the file was over 2 gig.

Dermmy - Oh I see how you arrived at that number, take 3521 away from 5702. If I wanted to extend the map with other dems then who would I work out the other heights relative to this one?

Btw could some kind soal please point me in the direction of a tutorial about merging dem maps in microdem, I once had it bookmarked but is not throwing up a 404 error message

Thanks for all the help guys

:Y:

Andy

 

[Dermmy]

Dermmy - Oh I see how you arrived at that number, take 3521 away from 5702. If I wanted to extend the map with other dems then who would I work out the other heights relative to this one?

Andy

Just keep reducing the absolute height by the same margin and it will all line up. A couple of thoughts come to mind though:

(a) at 1 gig in the raw route it will be close to impossible to finish anyway due to the time it is going to take and ...

(b) Trainz is going to have all kinds of problems merging routes that big. A better solution assuming you do in fact finish the first map would be to link to any second map using portals...

Andy

 

[RPearson]

Dermmy's way will work or the approach I told you will work but the way you did it originally won't unless the sea level reference elevation is actually used in the map.

Adding on to HOG generated maps is difficult because the geo referencing info is lost in the process. The correct height levels are the easiest part of it. In the range I used, +3000m in the DEM data is the reference level so all elevations are relative to that -> hrel = height -3000m. In Dermmy's the ref elevation is 3251m so hrel = height -3251m. For any new DEM just apply the ref elevation you used to it as I've done here. The same ref elevation has to be used for all.

That's the easy part. To align the DEM edges is not so easy in most cases. I don't believe there is any tutorial out there that covers seemless merging of HOG generated DEM maps. At this point I'm not prepared to go into any details but my 1st approach is to always merge DEMS in MD to cover all of the area of interest. Even if you have to crop these into managable areas you at least have a chance at a seemless merge. This is one area where the MD to HOG approach falls way short of using TransDem.

Bob Pearson

 

[Dermmy]

... I don't believe there is any tutorial out there that covers seemless merging of HOG generated DEM maps.
Bob Pearson

I don't believe a seamless merge between two maps is possible using HOG, at least not using Quad data as per the usual tutes. The map is generated using one 'corner' as a base and it is not possible to control where the diagonally opposite 'corner' ends up since the 'sides' of the route must finish up as multiples of 720 meters. Using seamless data it might be possible, but I have not tried.

That said I have never had a merge (even in mountainous country) which could not be 'fudged' in to a reasonable join.

Using TransDem I am pretty sure that seamless joins can be made...

Andy

 

[clam1952]

You can merge with microdem.

You use in the in out button on the top bar. This opens a blank window called data something or the other with a menu at the top.
Click merge on the menu bar.
Select Dems
Select Single pick
This opens a file open dialogue, browse to the first dem and select, the dialogue will open again, so browse to the next one and select and so on until you have finished merging dems, then click cancel on the file open dialogue.

This then opens a save dialogue, give the merged DEM a name and save, you should get progress bar as it merges and then it should open in the main window.
Then carry on as normal.

 

[geophil]

... [using HOG for Tibet] ...

Quick question: How do create your map overlays - since you are outside the US and do not have TIGER? The way they did it for the Darjeeling?

Once you have your route pegged out in TIGER style on top of the DEM, HOG can use this as a baseboard filter and may significantly reduce the .gnd file size. As merging HOG-made route modules in Surveyor is a challenge of its own - at least for mountainous terrain -, putting all of your route into a single but still manageable module is probably the best you can do.

 

[Dermmy]

You can merge with microdem...

Only up to a point. Once the image gets too large for Microdem to handle you need to create sub-routes and merge the routes in Trainz...

Andy