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Thread: Need help with earth obliquie projection

  1. #1
      Raphios is offline
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    Question Need help with earth obliquie projection

    Hey guys! it's been a couple years since I've posted anything. But I have a question for all the master cartographers out there. I have a gray scale bmp height map of planet earth that I wish to import into FT3 but I want to shift the axis so that the poles are in the tropics. I know that this can be done with a standard fractal generated map but to my knowledge this cannot be done once the world has been altered. The only solution is to import a height map that has already been altered beforehand. The only problem is that I can't an image that fits the specifications I want or a program that can alter the image without undesired effects.

    This is the bmp I have in mind...Need help with earth obliquie projection-srtm_ramp2.world.5400x2700.jpg


    And this is the desired shape that I'm after, but I just don't know how to get it this way.Need help with earth obliquie projection-tilted-world.bmp



    I got this image by using the program called Alternate World Map creator, It's a brilliant piece of software, I just don't know how to replicate it on the image that I want.


    If anyone can help I'd be really thankful

    Regards

    Raphios

  2. #2
      xoxos is offline
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    this similar thread http://www.cartographersguild.com/sh...ge-to-Mercator has a rec for 'flexprojector' which i haven't used. i don't know if it will let you change the orientation.

    the winkel projection has sinc functions, but most of the other projections i've noted have much simpler relationships between the spherical and 2d form, which would only take a bit of time with a steady head and an environment where you can read and write the data (eg. any programming language, matlab, octave).

    i'll check back in case no available softwares can be found.

    the other solution, since i'm guessing that's height field information you wish to use for a 3d app, would be to forget about everything below the water and use photoshop to drag the continents around and liquify/squish them to the new map using layers. only issue then would be you'd have to be 'creative' with the arctics.
    Last edited by xoxos; 05-13-2012 at 01:09 PM.

  3. #3
      waldronate is offline
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    The height map is the normal aspect of the Equirectangular projection. The image that you showed appears to be the transverse aspect of the same projection (also known as the Cassini projection). The oblique aspect allows you to put the north pole at an arbitrary location. There are liraries out there that should be able to do this (I think that the gdalwarp item in the GDAL package should be able to do so, for example).

  4. #4
      Laskaris is offline
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    Raphios, a big thank you to you for pointing me towards Alternative World Map Creator. I have been looking for a program exactly like that for ages.

    I would love to be able to do what you are asking for as well - take any map in the equirectangular projection and convert it to an oblique projection. Unfortunately, Alternative World Map Creator only does it with its preset world map. I would love to be able to load up my own map in the program, and convert it.

    So, it seems we are looking for the same thing.

  5. #5
      Laskaris is offline
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    Did you have something like this in mind?

    Need help with earth obliquie projection-tilted_earth_topography.jpg

    After some searching, I found a program which can do this. It is called Geocart 3. You can load any map image you have, as long as it is in equirectangular format, and convert it to other projections, including oblique ones with the top (or "pole") anywhere you want.

    The Demo version of the program inserts "Demo" watermarks into the exported map images, but otherwise appears to be fully functional.

    Good luck with your tilted Earth (which is what I believe you are trying to create). I love alternate, tilted Earths myself and might create a few myself. A nice exercise in climatology!
    Last edited by Laskaris; 06-03-2012 at 04:56 PM.

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      Gidde is offline
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    Does that software do Transverse Mercator? That seems to be the only projection I can't get any of my stuff to do.

  7. #7
      Laskaris is offline
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    Quote Originally Posted by Gidde View Post
    Does that software do Transverse Mercator?
    I think it does. There are several different Transverse Mercator Projections listed in the list of supported map projections.

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      Gidde is offline
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    Cool, I'll have to check it out! Thanks!

  9. #9
      Raphios is offline
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    Laskaris! You legend! Thanks heaps for pointing that software out to me, it's a huge help. I'm actually trying to set up a world for one of my novels I'm currently writing. However, in as much as I enjoy a good high fantasy romp every now and then, I have a distaste for how much belief has to be suspended in my own fiction. So when I write I try to remain as realistic as possible. And on a tilted earth, the sahara better not still be there when africa is sitting on the arctic circle. Thanks again for you help. And thanks to everyone for their imput! I'll be sure to send you guys copies of my finished work when I get the chance. And if I knew how, I'd send you some rep.

    Regards

    Raphios

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