Global Mapper v25.0

Projections: spherical/ellipsoidal Earth models

tjhb
tjhb Global Mapper UserTrusted 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_mapper
    global_mapper Administrator
    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
  • tjhb
    tjhb Global Mapper User Trusted 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_mapper
    global_mapper Administrator
    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
  • tjhb
    tjhb Global Mapper User Trusted User
    edited October 2010
    That is an immense help. Thank you Mike.