Projections: spherical/ellipsoidal Earth models
tjhb
Global Mapper UserTrusted User
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
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
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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 -
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 -
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 -
That is an immense help. Thank you Mike.
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