[Proj] WGS84 definition

[Martin Vermeer]

Dear List,

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

http://www.gps.gov.uk/guide4.asp

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 
geodesy. 

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
valid.

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

- Martin

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