Mercator

After falling down the learning curve for CC3+ a couple of times, I'm back around for another try. I thought I would practice with the various projects in the Cartographer's Annuals. Even if they are a bit too advanced for me, they give me a starting point.
My first obstacle is with the Mercator projection in the first Cartographer's Annual, (CA01). I elected to go with a real-world approach. I managed to download a binary file for Real-world Earth for FT3, and dropped the sea level to correspond to about the last glacial maximum to expose the various land bridges, and found a grid setting and a find a suitable projection to export into CC3+, with just the coastlines. Fine so far...but the whole globe gets exported, and what I need is the two hemispheres. I have an eastern hemisphere view and a western hemisphere view, but both these include the (severely distorted) other side of the globe as well. The instructions in the Mercator Mapping guide are incomplete. What am I missing?

Comments

  • MonsenMonsen Administrator 🖼️ 81 images Cartographer
    If you don't already have a projection called AE hemisphers in FT3, you can add it by following jslayton's instructions here.
  • ConfutusConfutus Newcomer
    Thank you! That's much better. Since this is Earth, to get a conventional Eastern/Western hemisphere view, I need to do the split about 20 degrees west of the prime meridian instead of on it. I've tried tweaking the parameters in the projection, but since I don't know exactly what they mean or do, I get strange results, none of them quite what I want.
  • ConfutusConfutus Newcomer
    On further experimentation, I find a problem is with the Western hemisphere: I can only get the left bound of the area of interest to -180 degrees: If I try to set it to -200 degrees, it cuts off at -180; if I set it to 160, it doesn't show the hemisphere at all. Apparently the projection computations do not comprehend the notion of slicing 20 degrees off one side of the map and moving it to the other. 8-)
  • MonsenMonsen Administrator 🖼️ 81 images Cartographer
    Seems like there are limitations in the projection code that prevents this.

    For a "regular" FT3 world, it is easy to rotate the globe just by changing the longitude of the north pole, but when it is made from a binary file, like I assume yours is since it uses earth data (I do assume you imported the earth data rather than draw it yourself from scratch), it isn't quite that easy.
  • ConfutusConfutus Newcomer
    Yes, this is the version with imported data from a binary file. I do have another version where I am trying to transform irregular blobs into recognizable continents, but with what I know how to do, that's taking a lot more work in finding and computing the screen positions of appropriate control points, (using Google Earth as a reference) and moving the nodes around. My sketching skills are sufficiently abysmal that I hardly dare scrap it and start over.
  • MonsenMonsen Administrator 🖼️ 81 images Cartographer
    The developer mentioned it may be possible to export it to Wilbur, do a toridial rotation, and then export it back. This isn't something I've attempted myself though, so I don't have a ready recipe.
  • ConfutusConfutus Newcomer
    Hmm. I haven't tried Wilbur at all, and I'm not entirely sure I want to just yet. That's a definite maybe.
  • jslaytonjslayton Moderator, ProFantasy Mapmaker
    Try this for the AE Hemispheres projection in Projection.txt:


    Projection 91, "AE Hemispheres"
    Scale 1.0
    Description "Azimuthal Equidistant Hemispheres"


    Segment "Azimuthal Equidistant", 0, -110, 0, 0, 1, 0, 0
    scale 1, 1
    Offset -0.5, 0.0
    Effective -180, 90, -20, -90
    Rotate 0
    EndSegment

    Segment "Azimuthal Equidistant", 0, -110, 0, 0, 1, 0, 0
    scale 1, 1
    Offset -0.5, 0.0
    Effective 160, 90, 180, -90
    Rotate 0
    EndSegment


    Segment "Azimuthal Equidistant", 0 70, 0, 0, 1, 0, 0
    scale 1, 1
    Offset 0.5, 0.0
    Effective -20, 90, 160, -90
    Rotate 0
    EndSegment

    EndProjection




    This is centered on -20 degrees (probably the opposite direction from what you intended). The important idea here is that the hemisphere that won't show everything gets changed into the original part plus a sliver.
  • ConfutusConfutus Newcomer
    YES! That is exactly what I wanted, and in the right direction, too. It had actually occurred to me to add in that slice as another segment, but I didn't know how to do it. BIG thank you.
  • ConfutusConfutus Newcomer
    As additional thank you, this is as close as I can get to what I was trying to do.
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