Matching and splitting .DT1 elevation to match imagery

deandean Global Mapper UserPosts: 2
edited September 2014 in Elevation Data
Firstly i hope im posting this in the correct place, im new to global mapper.

I am trying to match a DT1 elevation data file to a grid of images and i have not been able to find any similar posts or attempts by other people so thought i would ask how the best method is to achieve this.

I would like to be able to load a single DT1 file, convert it into grey scale based on height and then export it to png/tif etc... but i would like to split the exported files into a grid of images so i can use them as height maps for the satellite imagery i have.

Is this possible in Global Mapper? Any tips on how to do this would be very helpful

Comments

  • Thea_bmgThea_bmg Global Mapper User Posts: 38
    edited September 2014
    Hi Dean,

    Do your imagery files have an index grid (a shapefile or other vector data file showing the boundaries of your image tiles)? If so, you can load the index DT1 file and index grid in to Global Mapper, and change the shader drop down to be a 'Gradient Shader', which will be grayscale based on height. You can select your grid using the digitizer tool, and then go to File > Export > Export Elevation Grid Format, and select a file type such as GeoTIFF. Under Tiling, select the option to 'Use Selected Area Features for Tiles.' This will create a grid of geoTIFFs with the same boundaries as your images.

    If you do not have a grid, and you know the dimensions of your imagery tiles, you can create one using the Grid tool in the digitizer toolbar.

    Hope this helps,

    Thea
  • deandean Global Mapper User Posts: 2
    edited September 2014
    Hi Thea,

    Thankyou for your reply and sorry about the late reply. I have been checking that it all works correctly and it appears that it is! I had to push the exported Geotiffs through a few different programs in order to get them into Unity 3D with a usable heightmap so this is why its been a few days.

    One odd thing I have noticed when inside Global Mapper the scale said from 0m - 250m for the entire terrain however when exported and the heightmaps were built (using 0 - 250m scale) tiles next to each other had huge variations in height. I was wondering if the height is normalised for each of the split tiles? If so is the data for the min/max height of an exported geotiff is available? Had a look inside the Geotiff and couldnt find the data but i may have overlooked it. Hopefully i've explained this well enough

    Thanks,
    Dean
  • DMcKittrickDMcKittrick Global Mapper Trainer Posts: 58Trusted User
    edited September 2014
    Dean,

    The height should not have been 'normalized' during export. After exporting the tiles, try reimporting them into Global Mapper and in the Overlay Control Center, click the Metadata button to see the range of elevation within each tile. It is possible that the post-processing/converting that you performed after generating the GeoTIFF tiles, adjusted the elevation values.

    You might also want to check what other 3D formats your target software supports and try a different export format from Global Mapper.

    I hope this helps.

    - David McKittrick
    Senior Applications Specialist
    Blue Marble Geographics
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