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Thread: Equirectangular Projection controlling distortion with Tissot’s Indicatrix or similar

  1. #1

    Default Equirectangular Projection controlling distortion with Tissot’s Indicatrix or similar

    Are there any software programs that allow you to import an equirectangular projection and manually play with the distortion on it? I have an "almost" equirectangular map that is the result of a lot of work using unorthodoxed methods, going from 3d to 2d using a 3d scanner. The final process has resulted in an equirectangular projection that is 12 degrees off in distortion at the poles (they are too large), resulting in something between a mercator projection and an equirectangular projection(and I don't mean quantitatively). I'm looking to fix this by adjusting the distortion and making this a true equirectangular projection, the final result doesn't have to be exact, just close enough.

    Any help locating software that can do this and any pointers are welcome!

    Thanks!

  2. #2
    Administrator waldronate's Avatar
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    Sadly, it looks like http://flexprojector.com/ doesn't do raster things. Otherwise, it would pretty much be what you want.

    You might be able to use a georeferencer-type piece of software to do this. QGIS has such a plugin, I'm told.

    Something like Photoshop's warp tool might work. Or its perspective tool (basically, select the area with the distortion and stretch one side until it's what you want). I would recommend doing this to another layer with slightly more area selected than you need, followed by a nice blend between the two to avoid any discontinuities.

    If you find something that works for you, be sure to report back about how you did it.

  3. #3

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    Quote Originally Posted by waldronate View Post
    Sadly, it looks like http://flexprojector.com/ doesn't do raster things. Otherwise, it would pretty much be what you want.

    You might be able to use a georeferencer-type piece of software to do this. QGIS has such a plugin, I'm told.

    Something like Photoshop's warp tool might work. Or its perspective tool (basically, select the area with the distortion and stretch one side until it's what you want). I would recommend doing this to another layer with slightly more area selected than you need, followed by a nice blend between the two to avoid any discontinuities.

    If you find something that works for you, be sure to report back about how you did it.
    Photoshop Edit/Transform/Warp worked for me! I also used some post it notes for evening up the lines. Thanks again Waldronate! This was a vastly easier problem solution than I thought possible, so fun to learn something new about Photoshop.

    Cheers!

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