Projections: spherical/ellipsoidal Earth models

tjhbtjhb Global Mapper UserPosts: 454Trusted User
edited October 2010 in Technical Support
Mike,

Is there an easy way of knowing which projections in GM are implemented using an elllipsoidal Earth model, and which use a spherical Earth model?

This is proving important to us for using GM in a workflow with other products (and other cartographers).

We could probably test this without too much trouble, but perhaps there is already a list—or you might say that GM follows (e.g.) proj.4 in all cases.

As another alternative, perhaps I could give you a list of perhaps 8 to 10 projections that we'd especially like an authoritative answer on.

Tim

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited October 2010
    Tim,

    There isn't a list off-hand, although the vast majority of projections in Global Mapper use an ellipsoidal model. Global Mapper internally uses the USGS GCTPC library and PROJ4 for its projections. If you have a particular projection you are interested in I can check.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • tjhbtjhb Global Mapper User Posts: 454Trusted User
    edited October 2010
    Thanks very much Mike. Here's a list of the projections we're most concerned about right now. If this is too many, I think I can test manually.

    Mercator
    Miller
    Eckert IV
    Orthographic
    Polar Stereographic
    Lambert Azimuthal Equal Area
    Lambert Conformal Conic
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited October 2010
    Here are the types:

    Mercator - ellipsoidal
    Miller - sphere
    Eckert IV - sphere
    Orthographic - sphere
    Polar Stereographic - ellipsoidal
    Lambert Azimuthal Equal Area - sphere
    Lambert Conformal Conic - ellipsoidal

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • tjhbtjhb Global Mapper User Posts: 454Trusted User
    edited October 2010
    That is an immense help. Thank you Mike.
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