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dreamslayerx

OpenGL How do you read in Digital Elevation Model (dem) data from usgs.gov

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Hi guys. I am trying to replicate some terrain and display it with OpenGL I am getting the data form http://seamless.usgs.gov/ then I go to Tools to Access Data then select the seamless viewer. The next part is a little strange to me. I know how to select my area, and I want the elevation data. Alot of sites says that the data suppose to be outputed as ascii format, but I cann't read the files with word pad or notepad. Better yet its so many files I don't know which to even get the data from. Since I am new to this. I am trying to get the vector data for the elevation and have it in ascii format so that I can know what I am looking at to read the data in. Does anyone know how to do this? The national map seamless server address is http://seamless.usgs.gov/website/seamless/viewer.htm. The goal is to get the elevation data into a vector format so that I can read it into opengl to generate my terrain. Let me know if you guys know of some better approaches as well but I need to work with the digital elevation model (dem) data. Thanks for the help.

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Is this a link to a direct download for the converter, or do I have to download GRIDASCII to be able to convert the data? If so where can GRIDASCII be found, I googled it but didn't get a download link, so I'm assuming its within another program.


It's a feature of ArcView, a component of ArcGIS. You have a few options (in rough order of practicality) that I can see:

  • see if the 'developer tools' listed on the Esri website contain anything useful
  • search for an alternative parser, knowing the name of the format; the 'GDAL driver' links at the bottom of the Wikipedia article look helpful
  • buttonhole a geo-oriented friend at an academic institution to convert it for you
  • write your own parser using the information on that webpage
  • license ArcGIS at significant cost (thousands of dollars)


    Alternatively, the USGS NED FAQ suggests that it may be available in other formats from other sources. (Maybe try alternative - lower - resolutions if they'll suffice?) Sorry I can't help more. I've only used this format via ArcGIS, and USGS seems to have changed their format at least twice since I last used them.

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[quote name='dreamslayerx' timestamp='1317148895' post='4866523']Is this a link to a direct download for the converter, or do I have to download GRIDASCII to be able to convert the data? If so where can GRIDASCII be found, I googled it but didn't get a download link, so I'm assuming its within another program.


It's a feature of ArcView, a component of ArcGIS. You have a few options (in rough order of practicality) that I can see:
  • see if the 'developer tools' listed on the Esri website contain anything useful
  • search for an alternative parser, knowing the name of the format; the 'GDAL driver' links at the bottom of the Wikipedia article look helpful
  • buttonhole a geo-oriented friend at an academic institution to convert it for you
  • write your own parser using the information on that webpage
  • license ArcGIS at significant cost (thousands of dollars)

    Alternatively, the USGS NED FAQ suggests that it may be available in other formats from other sources. (Maybe try alternative - lower - resolutions if they'll suffice?) Sorry I can't help more. I've only used this format via ArcGIS, and USGS seems to have changed their format at least twice since I last used them.
    [/quote]


    I think that I am going to go the route of create .obj terrains from blender, but is there anyway that dem data can be converted into .obj format with a some form of downloadable converter? Do you know of any?

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I don't know of any off the top of my head, sorry. That's not to say that they don't exist, though.


Thanks for the help. I think the obj format is a good one since I can easily map the textures from a UV map of the terrain.

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