Terror forming - gaps in the world

[GSX1400]

I've been having problems with 'magic pyramids' and great white voids but this one is a doozie

I created 3D terrain using the "How to creat 3D terrain in 5 easy steps" tutorial and all seems to work OK apart from these pyramids.

I decided to download Mosaic, aparetnly the terrain editor of choice and the very first thing it showed me was why I'm having terrain troubles. There's a whole missing triangular section which extends right the way across my route forming an very large kind of "X". Have a loog at my screen shot. . . http://byfiles.storage.live.com/y1p17-C ... nye0xqAh0A

Or blog http://devizescastle5050.spaces.live.com/

I have been back to my original 3D Terrain only very first no-tracks at all backup and it appears that this is in fact a gap in the 3DEM data so I may well be stuffed and have to do this by hand.

If anyone has any suggestions other than manually building a terrain, they'd be most welcome.

[GSX1400]

I think I'm stuffed

I just GRE's and Demex'd from scratch and as you can see, the error is within the 3D Terrain data from America. Good job they didn't load any cruise missiles with it!

Have a look at the screenshot
http://ifg1aa.bay.livefilestore.com/y1p ... _demex.jpg

[NicolaFan06]

Honestly, DEM data is overrated unless you're able to get really high res stuff, I wouldn't worry yourself too much over it. As long as you have gradient data for the track, you can still do a good job of it.

I've always found the DEM data rather indistinct and lumpy, sharp inclines suddenly become rolling hills because the res is too low etc.

[GSX1400]

Is there a better way than using DEM data?

[terrycunliffe]

You can create terrain using the contour tool in TSTools. (assuming that you have the utility)
However, it is extremely tedious and time consuming to do, as effectively, you have to trace out the contours from the OS maps manually.

[dkightley]

Other than Terry's sugestion...Not really......unless you class taking a theodolite and a pair of hiking boots on a field trip as a way of getting terrain height data.

The freely available DEM data from NASA is the best free data available. If you have several thousand pounds spare, I'm sure you'll be able to purchase more accurate data.

When you said you followed the instructions in the sticky thread, you didn't indicate which exact source you obtained the DEM file from. I'm not sure if they're the same .....but the source file obtained via Google might be different to the file obtained direct from the ftp site. It might be worth a check...just in case....as the fault you seem to have looks like the data file stopping (or being clipped) a few hundred yards short on the rhs extremity.

[GSX1400]

Terry, thanks for the suggestion, I don't have TSTools and so I don't think I'll go down that route (pun unintended )

Doug, wellies and a theodolite on a wet hillside near the Salisbury plain isn't where I'd like to be. I don't want to appear unwilling or lazy but I have to draw the line somewhere

To be honest, I can't remember where I got the data from, I followed all of the links in "Terraform your UK Route in 5 Easy Steps [using DEM data]" until I found one that works. To be honest, watching the developments in SRTM is not something I have been doing so I don't know how up to date my terrain is.

If there is a newer better source, you mention Google, I'd love to try it out, it can only be an improvement.
If there is a link, please can you post it?

I think it would be useful for the article "Terraform your UK Route in 5 Easy Steps [using DEM data]" to be updated to reflect the currently available data sources as it takes a while to find a link that works and even then I think I got sent to NASA and a Northern American terrain only site.

I don't want to sound critical, this forum, its articles and this kind of dialogue with you guys is the best source of information I could get. I wouldn't have got anywhere near as far as I have without this help and support.

[leveritt]

To be honest, I can't remember where I got the data from, I followed all of the links in "Terraform your UK Route in 5 Easy Steps [using DEM data]" until I found one that works.

After looking at your screenshot, I would guess that you got the data from one of the old "one degree squares" sites. The tell-tale would be the skewed north-south boundary caused by the Goode Projection that Kuju chose, rather than the more useful Universal Transverse Mercator Projection.

The SRTM data has been available on the "seamless" site for quite some time. There you can get a one piece DEM. 90 m resolution DEM's are pretty small.

Go get ready, open your route in the RGE and mouse about to determine the lat/long extents of the DEM that you would like to have. You might write that down...

Go here: http://seamless.usgs.gov/ and click on "View & Download International Data". After the map loads, on the right select "Elevation" then tick "SRTM Finished 3 arc sec Shaded Relief". You should now see that the grayscale coverage of this dataset includes the UK.

Since you know your lat/long extents, you don't need to zoom in by clicking on the map, but you can if you wish.

On the left at "Downloads", hover the cursor to locate the "Define Download Area by Coordinates" button. Click on that to get a pop-up to enter your lat/long; at the bottom click on "Switch to Decimal Degrees" first. After entering your lat/long, "Add Area".

You may get another pop-up saying "There are no available products in the area that you indicated." If so, click on "Modify Data Request", scroll to the bottom to tick "SRTM 3 arc sec" and "Save Changes". When you see the resulting download page, make sure the Output Format is GeoTiff. If it says ArcGRID, "Modify Data Request" again to scroll down and make the change.

Seems cumbersome at first, but it works well once you've done it. If you have registered DEMEX, it just by-passes all of that and just goes directly to the download. The download obtained that way is to the correct format and is exactly tailored to your route's quad tree.

The "Terraform your UK Route in 5 Easy Steps" topic has been around a long time, and much "evolution" has occured. It's probably difficult to pick out the latest and best methodology.

regards,
charlie

[GSX1400]

This message has been edited by a Moderator

Charlie you are a diamond geizer

I have terrain, I have no pyramids If I was allowed to use rude worsd they'd be [Moderator Comment: dkightley - And, not surprisingly, you're not! So don't!]briiliant"

Just got to recut my cuttings and embankments but that's not a problem, they needed sorting anyway.

I think your instructions should be 'stickified' because it simply works!

Well done - I'm so happy.

This message has been edited by a Moderator

[leveritt]

Well that's just great. The data on the "seamless" site is based entirely in the old "one degree squares" data, however they went to great lengths to assure that there were no discontinuities, holes and spikes before releasing.

I think your instructions should be 'stickified' because it simply works!

But it already is, and you actually make my point about what's buried in the eleven pages of "Terraform your UK Route in 5 Easy Steps". It must be difficult for someone who has never approached this before to decide on the best method for their situation. Fifteen months ago with a report that it worked then:
http://forums.uktrainsim.com/viewtopic. ... 60#p740360

regards,
charlie