DEM from grayscale gridded elevation image?

tim53tim53 Global Mapper UserPosts: 68Trusted User
edited April 2010 in Technical Support
I would like to quickly generate 3D views of HRSC (High Resolution Stereo Camera on Mars Express Orbiter) images (.ND3) on their corresponding DEM files (.DT4) in Global Mapper 11. The DT4 files are grayscale images with the DN values corresponding to elevation in meters. How do I get global mapper to recognize the DT4 files as elevations?

-Tim.

Comments

  • tim53tim53 Global Mapper User Posts: 68Trusted User
    edited April 2010
    I should add that both the elevation file and image file were downloaded as PNGs.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited April 2010
    If the data is just a grayscale image, to get those grayscale values interpreted as elevation the only solution is to export to a grayscale BIL file, then load that back into Global Mapper. You should be prompted to treat the 8-bit grayscale BIL as elevation or imagery, at which point you can select to treat it as elevation data.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • tim53tim53 Global Mapper User Posts: 68Trusted User
    edited April 2010
    I exported the BIL file and reopened it, but didn't get a prompt about whether it's elevation or image data. It just opened the file.

    -Tim.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited April 2010
    Tim,

    Did you export it using the grayscale option for the BIL export?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • tim53tim53 Global Mapper User Posts: 68Trusted User
    edited April 2010
    No, I hadn't. I tried again and it did give me the dialog. But now the elevations are reversed (dark is high and light is low). Also, since the values are 8-bit, the ranges of elevation are -128m to +127m, which is a lot less than the actual elevation range.

    I downloaded the data from a site that may have converted the file to 8-bit from 16. I'll check on the PDS site for the .img version of the file...

    ...got it! Elevations seem to be correct!

    Thanks!
    -Tim.
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