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Xangis

Useful GIS Map Data for Terrain Rendering?

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Xangis    184
I'm working on an RTS project based on Vietnam. I would like to have accurate maps and I've been playing with GIS data, mainly the DTED Level 0 format (I even created a loader/converter for the format even though there are freely available viewer-converter utilities available just to get familiar with it). It's interesting, but not terribly accurate or high-resolution - in short, not exactly useful for what I want to do, which is generate a terrain heightmap for all of Vietnam. In fact, if you compare DTED Level 0 side-by-side with Google Earth, GE wins hands down. I see there are quite a few GIS data formats available (DEM, NED, DLG, E00, GTOPO30, NLCD, LULC, SDTS) and "the good stuff" appears to be either for military use only or part of hyper-expensive private datasets, and much of the data contains information that only pertains to the US and its territories. What I would like is something with a resolution better than 30 arc seconds. Something like 3 arc seconds might be ideal. Something that contains ground cover information or maybe a pair of datasets that I can combine to get heightfield information and ground cover information would be best. Any recommendations? What are my options for data in the $60 or less price range? Is there anything freely available that is likely to suit my needs? (I'm using the Torque engine, so any information that would be specific to that engine would also be helpful) Cheers, Xangis

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Guest Anonymous Poster   
Guest Anonymous Poster
You definitely should have a look at SRTM. See for more information: http://www2.jpl.nasa.gov/srtm/

Data is available at a resolution of 3 arcsec (~92 m) for free. The range is -56 to 60 degrees latitude, which is about 80% of the earth land mass.

There are a few issues however, the most important being that the data can contain voids, which can be quite large (hundreds of pixels). This happens due to "radar shadows" (high terrain obscuring radar signals from lower laying terrain) or the type of terrain (not enough signals were returned to accurately calculate the elevation, like water and desert).

There are several tools to fill the voids. Some use other elevation data sources, and others just use interpolation. Keep in mind that void-filled data is not real world data. If the voids aren't a problem, then SRTM is by far the best data source.

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Xangis    184
Thank you, that is pretty much exactly what I'm looking for.

I take it that this is all raw data in 16-bit format since the 1201 x 1201 x 16bit size of data points adds up to 2,884,802 bytes and that's the filesize...

So I guess that's why I couldn't find a whitepaper detailing all of the header info.

Cheers,
Xangis

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Guest Anonymous Poster   
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Xangis: Yup, but there is documentation available, see ftp://e0srp01u.ecs.nasa.gov/srtm/version2/Documentation/

The_dannobot: the link you provided points to the same dataset. The data offered there is the same as SRTM v2 (void-filling, correction of oceans/rivers/lakes, spikes/wells elimination, etc). There is no need to order there, if you can download it from the SRTM site already, and don't care about the DVD's.

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