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Thread: Projection Issue: Interrupted Sinusoidal to Equirectangular

  1. #1
      Asis is offline
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    Default Projection Issue: Interrupted Sinusoidal to Equirectangular

    I've got a interrupted sinusoidal map (a gore map, I read somewhere), and I'd like to make it equirectangular. Problem is, I don't know how and I don't know where to look anymore.

    The map has 12 sections of 30°, and the WIP thread is here. I will also attach the map at the end of this post.

    While I have come across a couple of promising looking projection programs, I haven't had much luck with them. I just can't get my head around Geocart, though it does look like it can do precisely what I want it to do. I was trying out the demo, so that may have been why I didn't get it to work. waldronate's ReprojectImage does do sinusoidal, but not an interrupted one (at least not as far as I can see).

    I've seen GDAL and QuantumGIS mentioned, but I have no experience in using a command line interface, and I'd rather not look around for ages and try to learn a new software if it turns out it can't do what I'd like after all.

    Other projection software I've come by only accept equirectangular (which is why I want the projection in the first place).

    Maybe I'm just being slow and the answer to this is right in front of my eyes. If you know how, please do tell. I'd really appreciate it.
    Attached Thumbnails Attached Thumbnails Projection Issue: Interrupted Sinusoidal to Equirectangular-scan.png  

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      Hai-Etlik is offline
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    Well, ultimately it's just parts of 12 sinusoidal projections, each with a different central meridian. You should be able to break it apart, reproject each independently, and then combine them.

    Also QuantumGIS is not a command line tool, though it uses Proj.4 for its projection implementation, which doesn't support interrupted projections.

  3. #3
      Asis is offline
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    I hadn't thought about breaking it apart and doing it in sections. Sounds messy, but doable. Thanks for the suggestion. I'll go try it out.

    I know QuantumGIS isn't. The having no experience with command line interface was only referring to GDAL. I see now that I could have been a lot clearer. My apologies.

    Thank you for a quick reply, by the way.

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      waldronate is offline
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    Squishing, slicing, and pushing the pieces back together again would give you something like that shown below (the black parts are the artifacts from a slightly imperfect alignment when reprojecting).

    Projection Issue: Interrupted Sinusoidal to Equirectangular-assembled.png

  5. #5
      Asis is offline
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    Hehe, yeah. That's pretty much what I got as well. Wonderful software, waldronate. Thanks.

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