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Thread: bitmap to lat/lon

  1. #1
      Pyer is offline
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    Question bitmap to lat/lon

    first of all, I'm not looking for an automatic conversion tool.

    I got bitmap maps of a fantasy world and I would like to have a lat/lon file of coast/ rivers/ etc. (the bitmap has lat/lon grids).

    my first idea was to use the bitmap as a background image in a vector program (inkscape? DrawPlus?), draw vectors along the requested parts (coast, rivers, etc.), then convert the resulting vectors into lat/lon (ie. CSV file). but well, I'm a bit lazy and would prefer not to have to write the SVG to latlon program and was wondering if any of you had a better idea to solve my problem ?

    TIA, Pyer

  2. #2
      Redrobes is offline
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    Hmm bit of a tricky one that. If it were me, which means you need a little bit of fairly simple coding in say python or perl, then I would do those shapes in inkscape and save the file in the standard inkscape shapefile format. That format is mainly made of splines which are a pain to deal with. So you can take that file and import it into Blender which has a special import for inkscape files. It will convert them into lines and points for you. From there you can save the file in another format - I would pick the OBJ format since its a text file. Now this is where you need to code, for you will have some arbitrary scale. So if as part of your map you put in some extents lines as well as the coast - like a box border, then you can pick up all these numbers in the OBJ file, run through them and get extents information. Then assign some extents lat longs to it and just scale them all and print them out in CSV.

    This is fairly similar to what I do in reverse for the guild members map. In there you enter the lat long and each map bitmap has preset lat long extents information and it scales it back to pixels and puts your pin in the map there. See my sig for the members location page.

    What you are asking for tho is basically a GeoRefferencing application. If you have the money then Global Mapper is great but there are some free ones as well. I think QGIS might do that job but I am no expert in GIS apps. So try this link and have a play with it:

    http://www.qgis.org/

  3. #3
      Hai-Etlik is online now
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    Redrobes is right, you could do this in QuantumGIS using its Georeferencing and Digitizing capabilities. It is going to be a bit of work, both to learn to use QGIS, and to actually do the digitizing.

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