Global Mapper Pro

Creat new datum based on mapinfo affine transformation parameters

herbamatic
herbamatic Global Mapper User
edited April 2012 in Projection Questions
Hi,
I'm a dual Mapinfo/GM user and would like to add a custom projection I have define in mapinfo to the global mapper add datum. This way I can display grid up in my local grid. The grid is a UTM grid that is affine transformed/rotated from WGS84 (no z change though) and in meters.
in mapinfo its defined as
[FONT=&quot]name, projectionnum + 3000, projection parameters, unitnum, A, B, C, D, E, F, x1, y1, x2, y2[/FONT]

the A and B are x "rotations" with C the translation. D, E are y "rotations" with F the translation
x1, y1, x2, y2 are just the bounds where its valid.

Is it possible to somehow use these, or do I have to recalculate all the parameters in a different format to be able to use something like the 3 or 7 parameter transformation.

Thanks.

Comments

  • global_mapper
    global_mapper Administrator
    edited March 2012
    What you have actually sounds more like a generic coordinate transformation more than a custom datum. Try right-clicking on a layer in the Control Center in Global Mapper and selecting to transform the coordinates, then select to provide a custom transformation with a scale, offset, and rotate and see if you can use that to define the transformation that you want. It sounds like yours may be slightly different than what GM supports, but maybe you are just using different terminology.

    Thanks,

    Mike
  • herbamatic
    herbamatic Global Mapper User
    edited March 2012
    Yes, it is a generic coordinate transformation, I guess I should not have used the word datum.
    When I open the files, and GM asks what projection, I would like to select this custom projection so that grid north is up in GM, and such that other files I might open in say UTM WGS84 will overlay properly. I was hoping to define something so I would just be able to select it in the choose projection dialog.
    is "right-clicking on a layer in the Control Center in Global Mapper and selecting to transform the coordinates," a feature in GM13? (I only have 12).
    thanks
  • global_mapper
    global_mapper Administrator
    edited March 2012
    Yes the generic transform feature is new in v13. There is also support for saving a defined transform to a file (.gm_xform) that you can place in the same folder as the file and have that transformation automatically applied to the coordinates in a vector file when you load it.

    You might download the latest trial of Global Mapper from www.globalmapper.com and see if that works for you for your data.

    Thanks,

    Mike
  • kfroese
    kfroese Geotechnical Engineer Trusted User
    edited April 2012
    This is a fantastic feature! I found this thread searching for a method by which to take my plant grid drawing with only one common point with UTM. It work excellent.
    Any chance of being able to do the reverse and convert my workspace to plant grid? That would facilitate printing stuff on this project since plant north is 50 degrees rotated from UTM north.
  • global_mapper
    global_mapper Administrator
    edited April 2012
    If you can define a projection that is your plant grid you can just set that up on the PRojection tab of the Configuration dialog. If you just want something rotated at a particular angle and don't actually need the XY coordinates to match, just select an Orthographic projection and set the center latitude and longitude to the center of your projection area and set the rotation angle to 50 degrees (or whatever you need).

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
  • kfroese
    kfroese Geotechnical Engineer Trusted User
    edited April 2012
    Ha! That was what I was looking for. Thank you.

    Suggestions:
    -Allow scale factor on this projection? I can almost match my plant grid but since it is based on a pure rotation of UTM, the distances aren't quite right since I can't set a scale factor.
    -Allow a similar type of rotation in plotting? That would allow me to print based on a local rotation to fit the page better.
    -Allow several sets of these that can be interchangeably used? I have another project where we have identified several different areas for analysis were being able to quickly select the rotation would allow printing of these areas to be much faster than having to load custom .prj from files for each zone.

    Thanks again for prompt and effective support responses.
  • global_mapper
    global_mapper Administrator
    edited April 2012
    Ah yes the Orthographic projection doesn't have a scale factor. If you need that I would suggest using Transverse Mercator instead and do the same thing as far as centering the projection on your map, then you can also provide a scale factor.

    Any rotated projection that you are using should work just fine when printing as well. Your printout should look the same as what you see on the screen. We do eventually plan on adding generic rotation capabilities though for rotating a view independent of a projection.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    http://www.globalmapper.com
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