[Proj] WGS84 definition

Clifford J Mugnier cjmce at lsu.edu
Mon Dec 5 14:57:27 EST 2005

Dear Martin,

I think such lofty declarations are a bit out of the ballpark for PROJ4
users.  PROJ4 does not claim to be the torchbearer for the "total answer to
Computational Geodesy."  Which reference frame is used should be restricted
to the user's conscious choice (if any), of their data and the concomitant
metadata associated with that choice.

My guess is that most PROJ4 users couldn't care less about reference frames
and the (very) basic foundations of coordinate systems and reference
frames.  For those that DO care, they should be capable of recognizing the
differences between map projection implementations and the necessary datum
shift algorithms and associated shift parameters.  PROJ4 is not intended
ONLY for Europe, so provincial declarations are more confusing to the
neophyte than helpful.

Merry Christmas,

Clifford J. Mugnier
Chief of Geodesy
Department of Civil Engineering
CEBA 3223A
Baton Rouge, LA  70803
Voice and Facsimile:  (225) 578-8536 [Academic]
Voice and Facsimile:  (225) 578-4474 [Research]

Dear List,

I found a nice explanation of the various realizations of WGS84 at the


I am sorry if this has been asked before, but what is the WGS84 that
proj4 (and GIS software in general) refers to? Of course this only
matters at the better than dm level, so is really only meaningful for

The most sensible thing, I think, would be to refer to a realization
fixed to the local crust. I.e. in Europe, ETRF89. That way the
transformations are not time dependent -- though also not globally

Does this question have an answer, or a policy, within proj4?

- Martin
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