Winkels projection

BrauneBraune Global Mapper UserPosts: 11
edited October 2007 in Projection Questions
Hi,
I would like to know if it is possible to add projections in global mapper and if so, how it can be done. The reason is, that I would like to georeference some atlas maps of the world, which are projected in "Winkels" projection. I cannot find this projection in Global Mapper. Can anybody tell me what has to be done to add projections?
Thanks and greetings,
Erik

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited August 2007
    There is not any way for users to add new core projections to Global Mapper. Those have to be added by us. It does look like we could pretty easily add support for projections called Winkel I and Winkel II. There is another projection called Winkel Tripel that we would not be able to easily add support for. Is either Winkel I or Winkel II the projection that you are needing?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • BrauneBraune Global Mapper User Posts: 11
    edited August 2007
    Hmm, I don't exactly know which projection it is, but I think it is Winkels I. It would be great if you can provide me with this projection.
    Thanks for your immediate support!
    Greetings,
    Erik
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited August 2007
    Erik,

    I have gone ahead and added support for the Winkel I projection to a new build of Global Mapper. As we are about to release Global Mapper v9.00 next week, this new projection will be in that release. If you want to try it now, you first need to download and install the latest v9.00 beta from http://www.globalmapper.com/global_mapper9_setup.exe . Then you need to download the new build with the projection at http://www.globalmapper.com/global_mapper9.zip . Simply download that file and extract the contents into your existing v9.xx installation folder to give it a try.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • BrauneBraune Global Mapper User Posts: 11
    edited August 2007
    A big "Thank you" for your immediate response. If all software developers would act this way, the satisfaction of the users would be in powers higher...
    Unfortunately, the projection of my map appears not to be Winkel I. The latitudes above and below the equator are bent upwards the borders of the map (In Winkel I they appear to be parallel to the equator). Therefore it appears to bei Winkel Tripel.
    There is another projection called Winkel Tripel that we would not be able to easily add support for.
    Hmmm, this doesn't sound good...

    Greetings,
    Erik
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited August 2007
    Erik,

    That's too bad. Unfortunately if the projection is Winkel Tripel we won't be able to add it as none of our projection libraries include full support for that projection.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • BrauneBraune Global Mapper User Posts: 11
    edited August 2007
    Hmm, really bad news. I've searched a bit in the internet. It appears to me that one of the problems is that it can't be calculated inversely (Don't know if I understood that right...).
    I've found this paper:
    Computer Program for the Inverse Transformation of the Winkel Projection
    J. Surv. Engrg., Volume 131, Issue 4, pp. 125-129 (November 2005)
    Perhaps this might help? I think it would be great to be able to make use of Winkel Tripel in Global Mapper (not only for me), because the world maps from National Geographic are also created with Winkel Tripel projection.
    Greetings,
    Erik
  • BrauneBraune Global Mapper User Posts: 11
    edited August 2007
    Sorry, I forgot to quote the abstract of the paper:

    The map projection problem involves transforming the graticule of meridians and parallels of a sphere onto a plane using a specified mathematical method according to certain conditions. Map projection transformations are a research field dealing with the method of transforming one kind of map projection coordinates to another. The conversion from geographical to plane coordinates is the normal practice in cartography, which is called forward transformation. The inverse transformation, which yields geographical coordinates from map coordinates, is a more recent development due to the need for transformation between different map projections, especially in Geographic Information Systems (GIS). The direct inverse equations for most of the map projections are already in existence, but for the projections, which have complex functions for forward transformation, defining the inverse projection is not easy. This paper describes an iteration algorithm to derive the inverse equations of the Winkel tripel projection using the Newton–Raphson iteration method.

    Greetings,
    Erik
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited August 2007
    Well it sounds like that document may contain the required formulas for the inverse transformation, but I haven't been able to find a free copy of the document anywhere on the web. It looks like the cost for the document is a couple of hundred dollars, with no guarantee that the transformation described would be useful or easy to implement.

    Have you tried using one of the other built-in global projections, like Aitoff-Wagner or Robinson? Perhaps they will be close enough to fit your needs?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • BrauneBraune Global Mapper User Posts: 11
    edited October 2007
    Finally I managed to get a pdf copy of the paper mentioned above. I can send you a copy of the paper - perhaps you are able use it for the winkel triple projection...
    Shall I send it to the support@globalmapper.com adress?
    Greetings,
    Erik
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited October 2007
    Erik,

    Yes, you can send the document to support@globalmapper.com.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited October 2007
    Erik,

    I finally had a chance to implement the Winkel-Tripel projection specified in the paper that you provided. Everything seems to be working well now. I have placed a new build at http://www.globalmapper.com/global_mapper9.zip with the change for you to try. Simply download that file and extract the contents into your existing v9.xx installation folder to give it a try.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • BrauneBraune Global Mapper User Posts: 11
    edited October 2007
    Hi Mike,

    thank you very very much for the quick implementation. I've tried to do it with some maps and the result seem to be very promising. Only towards the left and right borders of the maps are slightly distorted. (I will send you a screenshot in a separate e-mail). The map image is taken from wikipedia. I selected 5 GCP for recifying the image. Finally, I exported the image to a kmz-file to view differences between the image and the google earth image.
    Any suggestions what went wrong? As far as I understand the projection/datum question, the image should not be distorted after rectification when the same projection is applied to the original map (at least this holds true for the maps I rectified before - equalarea conic projections).
    However, it is very valuable that I am now are able to use the winkel tripel projection with global mapper. Thanks again,
    greetings,
    Erik
  • BrauneBraune Global Mapper User Posts: 11
    edited October 2007
    Hi Mike,
    I've tried the winkel tripel projection with one of National Geographic's maps - it fits perfectly! Hence, the distortion seems to be intrinsic of the other maps I've tried before.
    Greetings,
    Erik
  • BrauneBraune Global Mapper User Posts: 11
    edited October 2007
    Another test with one of the maps that were distorted: Adding a large amount of GCP (about 50 Points) yielded results that were sufficient precisely! :D
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited October 2007
    I'm glad to hear everything is working well with the new projection. It will be included in the next release of Global Mapper for everyone to use!

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
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