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  1. #1
    Global Mapper User
    Join Date
    Oct 2010
    Posts
    2

    Default Best Projection for Cross-Sections

    I've been saving path profiles cut from a DEM as .xz distance elevation ascii text and loading into GM to draw geology on. What is the best projection to use in order to minimize distortions for 2D distances and elevations of several kilometers?

    thanks,
    Chris

  2. #2
    Administrator
    Join Date
    Jun 2007
    Posts
    16,451

    Default

    Chris,

    Make sure to choose a projection with linear units like meters and have your distance and elevation units set up as meters in Global Mapper prior to saving the .xz file. Then your X and Z units from the file (which become X and Y when imported) should be treated the same and measure properly.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com

  3. #3
    Global Mapper User
    Join Date
    Oct 2010
    Posts
    2

    Default

    Hi Mike, thanks for the feedback. I've been using a Mercator projection for the cross-sections, but realized there are distortions. The area of a 500x500m square with lower left corner at 500x,0y has an area of 251686 sq m instead of 250000 sq m. I understand why this is, but am having trouble picking an appropriate alternative. I've started using Equirectagular, which gives the correct area, but a quick google search says this projection has significant distortions as well, although perhaps not significant at the scale I'm working in. Is there a better approximation of purely Cartesian coordinates for working within 5000m of 0,0?

    Thanks,
    Chris

  4. #4
    Administrator
    Join Date
    Jun 2007
    Posts
    16,451

    Default

    Chris,

    For something that small I would use a Transverse Mercator or Orthographic projection centered at the area center. There should be negligible distortion for an area that small with either of those projections.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com

 

 

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