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Thread: Help with map projections

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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:

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    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:

    Click image for larger version. 

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    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):

    Click image for larger version. 

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    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
    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
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    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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