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Author Topic: Elevation data height  (Read 29354 times)

KelvinNZ

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Elevation data height
« on: April 14, 2012, 10:25:38 pm »
Hi Cameni,

what height elevation data is the standalone data? is it 90m SRTM and is this the highest possible data that is available for OT?
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cameni

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Re: Elevation data height
« Reply #1 on: April 15, 2012, 02:52:02 am »
It's derived from 90m SRTM. Thus far it's the only global dataset available. There's also ASTER that should be 30m, but it's got too many defects to be usable yet.
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KelvinNZ

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Re: Elevation data height
« Reply #2 on: April 15, 2012, 03:38:48 am »
Ok. I have been reading quite a lot about the various data today and was wondering if OT would utilize higher resolution. I was reading the details about a newly released elevation data package for Microsoft Flight Simulator and Prepar3d which explains some manual adjustments made to the data to get it looking more accurate. See the link below if you are interested:

http://www.fly2pilots.com/cms/Ui/Pages/Products/MainPage.aspx?id=2d768af2-35f2-4107-8d22-5ddf9e193b47
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cameni

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Re: Elevation data height
« Reply #3 on: April 15, 2012, 04:42:26 am »
Sure OT could use a higher resolution of data, and we don't even have to resort to some hacks as the whole handling is in our hands. There are of course better source data that are commercially available, that we could use if it was economically viable for us as well.
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KelvinNZ

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Re: Elevation data height
« Reply #4 on: April 15, 2012, 06:16:52 am »
Cameni, if there is a website where you have seen this commercial elevation data can you point me to it?
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cameni

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Re: Elevation data height
« Reply #5 on: April 15, 2012, 06:51:52 am »
A couple of links can be found, for example, here. Else just search for elevation dataset [commercial]. Some references are at http://vterrain.org/
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KelvinNZ

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Re: Elevation data height
« Reply #6 on: April 16, 2012, 03:12:17 am »
Hi Cameni,

Can you confirm if the SRTM data used in OT is the same as noted here:
http://srtm.csi.cgiar.org/

it appears to be version 4, is this the same version used in OT?

What do you think about this site:
http://www.diva-gis.org/Data

it has all sorts of data per country (global data). Is it possible and practical to draw information from the downloadable files?

See the attachment for the areas that are covered.
« Last Edit: April 16, 2012, 03:29:24 am by Kelvinr »
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cameni

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Re: Elevation data height
« Reply #7 on: April 16, 2012, 03:27:42 am »
No. That one doesn't have a suitable license for us. Besides, it also doesn't contain data for areas above 60° north. We used http://www.viewfinderpanoramas.org/dem3.html data which is based on the original SRTM.
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KelvinNZ

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Re: Elevation data height
« Reply #8 on: April 16, 2012, 04:19:13 am »
Cameni,

Can you tell me how I need to be reporting the elevation issues using xnview and the plugin? The only data I have is the Southern Alps not New Zealand in its entirety. If you could let me know what you need to be seeing from this then i can start trying to note all the incorrectly elevated areas in the data.

EDIT:

I was wondering about a more practical way to determine elevation problems in the SRTM data maybe by running a side by side application to compare using OT
« Last Edit: April 16, 2012, 04:36:25 am by Kelvinr »
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cameni

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Re: Elevation data height
« Reply #9 on: April 16, 2012, 04:37:49 am »
You can download the tiles from http://rmw.recordist.com/ specifying a lat&lon window. Xnview with the plugin is one way to view the terrain data. If you find an improper terrain in OT, you can locate it in the source files using the lat&lon coordinates.

Then we would need to fix it. A full fix can be costly (in terms of time), but a simple fix could be possible - depends on the type of the bug. I'll ask ME-DEM guys what software could be used to fix these issues the easiest way.
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KelvinNZ

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Re: Elevation data height
« Reply #10 on: April 16, 2012, 05:05:44 am »
That sounds good. If it is merely a repetitive process and just time heavy then I wouldn't have any issues working through the errors; given that no major programming needs to be done to fix each error. I have quite some spare time I can invest and happy to help, not to mention that i have always had an interest in this sort of thing.
« Last Edit: April 16, 2012, 05:07:45 am by Kelvinr »
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monks

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Re: Elevation data height
« Reply #11 on: April 16, 2012, 09:45:35 am »
Aren't SRTM files already fixed? I mean, an attempt has been made to fix them.
 
SRTMv4 has been 'fixed' according to the various step described in the link but there will still be problems. I've not encountered any in Outerra but I've no doubt they exist.
http://www.cgiar-csi.org/data/elevation/item/45-srtm-90m-digital-elevation-database-v41

 I think you could get away with using Photoshop in png 16 bit format if you had auxillary dems that were not available to the folks who produced the v4. Blend the two terrains together. I'm not familiar with XNview -could you use that as a 3D viewer? Either way, you'd definitely need a 3D viewer to view your Photoshop work.
 You could convert between the png and the native via Wilbur, 3DEM, or I could do it for you here painlessly via Global Mapper.

 You could of course go track the areas down in Google Earth and eyeball their commercial terrain, and fix them manually but you'd need a 3D terrain package for that. I'd recommend Leveller, World Machine Pro or GeoControl. Wilbur is very capable and free!, but you're limted to 2D. Of the three, Leveller is the most paint friendly and there's a 64 bit version available now. 
I've basically done this kind of thing before. I blended manually between our project data and real world data. You wouldn't need the Photoshop stage (but then you might well already have that app), but I'd recommend Leveller to do it.

 A programmatic fix would be possible but I think they've already covered all those bases in v4 anyway.

 If you feed me the lat long coords or links to files I could open them up, merge them and export them in a useful format. Any chance of posting some pics of the dodgy areas Kelvinr?

monks
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foxfiles

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Re: Elevation data height
« Reply #12 on: May 14, 2012, 05:32:40 am »
Just FYI, Global Earth Coverage Available in 2014, TanDEM-X Global Digital Elevation Model, see here :

http://www.astrium-geo.com/na/1068-tandem-x-global-dem

But what price and which datas size for such an accuracy ? I wonder

 :D    I got the answer for the data size LOL :
" lying in close formation only a few hundred metres apart, the two satellites are imaging the terrain below them simultaneously, from different angles. These images are processed into accurate elevation maps with a 12-metre resolution and a vertical accuracy better than 2 metres. The amount of data generated by the satellites will grow to 1.5 petabytes within three years "

They have 3D Elevation10 (or 30) samples there too...Barcelona area
« Last Edit: May 15, 2012, 01:31:09 pm by foxfiles »
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monks

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Re: Elevation data height
« Reply #13 on: October 16, 2012, 08:04:50 am »
petabytes...? pfftt!  ???  I'm thinking though that the dem alone won't come to that. I mean at 100m res the whole Earth is around 15-20 GB? So 10x res should give you 150 GB surely. Hmmm, no, it's squared...so it's x10^2...which is massive but still "only" 1.5 TB.

monks
« Last Edit: October 16, 2012, 08:06:49 am by monks »
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cameni

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Re: Elevation data height
« Reply #14 on: October 16, 2012, 08:33:22 am »
I guess they mean the collected data from multiple runs, not the dataset size.

Raw input data at 90m come to ~80GB, resampled to ~76m & packed are ~12GB though we are losing some details by the bilinear filtering there.
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