[PROJ] Static/Dynamic Webmapping Problem version 2.0

[Martin Desruisseaux]

I did not yet had the time to follow this thread closely (will try to do
later), but I would like to react on some points:

  * In my reading of ISO 19111 §3.1.16 [1], the difference between WGS84
    realizations can be close to one meter. Note huge, but not
    irrelevant neither.
  * ISO 19111 §3.1.62 seems to define a static reference frame as a
    frame without time evolution, regardless if fixed to the plate or not.
  * In past emails I have seen WGS84 cited as a "dynamic datum". In my
    understanding, it is rather a "datum ensemble", which is not the
    same thing.

Useful quote from ISO 19111:

    “WGS 84” as an undifferentiated group of realizations including WGS
    84 (TRANSIT), WGS 84 (G730), WGS 84 (G873), WGS 84 (G1150), WGS 84
    (G1674) and WGS 84 (G1762). At the surface of the Earth these have
    changed on average by 0.7m between the TRANSIT and G730
    realizations, a further 0.2m between G730 and G873, 0.06m between
    G873 and G1150, 0.2m between G1150 and G1674 and 0.02m between G1674
    and G1762).

Regards,

    Martin

[1] http://docs.opengeospatial.org/as/18-005r4/18-005r4.html

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