Global Mapper v24.1

Solve for best ft coordinate system parameters given a set of coordinate values

WildT2 Global Mapper User
edited September 2013 in How I use Global Mapper
Assume I have a set of X,Y grid values that might be on an assumed and unknown projection. I also have geographic coordinates (LLH) that are reliably known to be on a published datum for each of these assumed X,Y grid values. Is there a way to associate the LLH values to the XY grid values to produce the Transverse Mercator projection that will best fit these grid values and have the projection parameters output as the resulting answer?


  • global_mapper
    global_mapper Administrator
    edited September 2013
    There isn't currently anything like that in Global Mapper, at least for trying to determine which projection parameters were used to convert a given set of LL values to XY. In most cases a common system, like UTM or State Plane (for US) was used, so a few educated guesses will find the answer, but there isn't anything to try and find the more general case where anything could have been used.


    Global Mapper Guru
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • kbellis
    kbellis Global Mapper User Trusted User
    edited September 2013
    WildT2 (what I learned to turn angles on :)

    Try this just for fun:

    Start a Global Mapper project - projection doesn't matter (as Global Mapper can easily deal with any of them), just use whatever your Lat and Long values you have. Choose and manually place a few well placed points; i.e., outside edges and center points of your project area using the Digitizer tool.

    Make an accurate raster (e.g., .jpg, .tif, etc.) plot of those same selected points in your assumed coordinate system and drop that into Global Mapper. It will immediately ask you to rectify and say YES!

    For extra fun, explore the various methods afforded Global Mapper users in resolving rectification.

    Once rectified you can project to anything you like using the Configuration, Projection tab dialog.


    PS. Here's a 10 minute video I made on Rectification.. many others here on the forum.