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Thread: Help with map projections

  1. #1
      Soixante is offline
    Guild Member Soixante's Avatar
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    Help Help with map projections

    Dear smart people,

    I need some help with the following: I have a map of a continent, like so:

    Help with map projections-test.jpg

    Please note, this is just an example, the real map is still a work in progress.

    The area covered by this map corresponds to the following area on a map of the whole world:

    Help with map projections-rough-world-reference4.jpg

    Roughly, this is between longitudes 23° W to 28° E, and latitudes 43° N to 4° N. Now what I want to do is to make small, regional maps from the map of the continent. Sort of like this (again, just an example):

    Help with map projections-test2.jpg

    However, I want to be able to change map projections when going from the continental map to the small regional maps. I also want to be able to add an exact graticule of meridians and parallells; it needs to be correct with the projection used and I want to be able to have a very fine graticule down to single degrees at the very last (preferably minutes).

    I have FT3, but the problem is I cannot seem to import a pre-existing shape/continent as a black and white image and then specify the latitude and longitude limits of the map, the projection I want to use, etc. If FT3 allows this I am not able to figure it out. I have also looked at some plugins for PS that allow to change the projection of an image, but of course then it's a destructive way of editing and they are not really suited for my needs, I think. I have also looked at G.Projector, a free software that was made specifically for changing projections, but I am not sure that it, either, can do what I want.

    I would really appreciate some advice and recommendations for which software could help me accomplish what I want to do.

  2. #2
      Hai-Etlik is offline
    Guild Expert Gracious Donor Hai-Etlik's Avatar
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    I'm not entirely clear on what you are after but I suspect you are getting into territory where you may need a GIS.

    I want to be able to have a very fine graticule down to single degrees at the very last (preferably minutes).
    G.Projector only has 2 degree graticules. In a GIS, you should be able to track down shapefiles of finer graticules; NaturalEarth has a free 1 degree graticule shapefile for instance.

    I cannot seem to import a pre-existing shape/continent as a black and white image and then specify the latitude and longitude limits of the map, the projection I want to use
    G.Projector can do this just fine.

    it's a destructive way of editing
    I'm not entirely sure what you mean here. If you want to be able to apply a bunch of graphical glitz, and then reproject it and have it come out looking OK, that's not going to happen. The best you'll get is working with vector data in a GIS where you can set up your symbology (which doesn't include all the filters and whatnot available in a graphics editor) and then you can reprojected the vector data, and the GIS will symbolize the projected data.

    This is the result of noodling around with your map in QuantumGIS
    Help with map projections-blah.png

    I've attached the shapefiles I made. It's pretty rough but it works. Learning to use a GIS is quite an undertaking though.
    Attached Files Attached Files

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