[PROJ] Could you please explain me why I can't project RDN2008 (EPSG:6706) to ERTF2000 (EPSG:9067) or ITRF2000 (EPGS:8997)

[Greg Troxel]

Even Rouault <even.rouault at spatialys.com> writes:

> For RDN2008, there are 2 transformations available:
>
> - one from RDN2008 to ETRS89 (EPSG:4258), with a null Helmert
> transformation and a accuracy of 0 m. This is consistant with how you
> described RDN2008, and this transformation has the comment "RDN2008 is
> the second Italian realization of ETRS89"

A far more lengthy way forward might be:

  Italian geodetic authorities (whoever defined RDN2008) publish a
  transformation from RDN2008 to some modern ETRFyyyy, including an
  error estimate.

  They submit that to EPSG for inclusion.

  A new EPSG version is published.

  A proj release arrives with the new EPSG version.

  Meanwhile, you wait for the previous 4 steps.

I realize it doesn't solve your problem now, but authoritative
transforms with tight error estimates shorten the transform pipelines
that are used and lead to better answers.  The above avoids ETRS89.

> Afaik, RDN2008 is ETRS89 realization ETRF2000 epoch 2008.0.

If you believe that precisely, you could just relabel your data as being
ETRF2000 (assuming the standard epoch is 2008.0).

Or insert a transform similar to Even's sugggestion, perhaps with better
accuracy.  I would expect RDN2008/ETRF2000:2008.0 to be at the 0.01m
level -- but I am pretty clueless about ETRF details.


  
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