[PROJ] Tie breakers used when ordering candidate operations

[Even Rouault]

> Related question: do you think the EPSG registry should include some
> kind of numerical "preference ranking" field to allow for better
> selection in ambiguous cases? Are you aware if this has ever been
> discussed before?

I believe nobody (maintaining a geodetic database) wants to go into that 
business of saying what is prefered or not. This depends on too many factors, 
and this would make the maintenance of the database even more complicated (I'd 
say that I have to notify IOGP about issues found by the PROJ import script 
for half of the recent EPSG releases). Furthermore, accuracy values in EPSG 
for a transformation involving the generic WGS 84 CRS are generally derived 
from accuracies of other transformations between plate-fixed CRS, and adding 1 
or 2 m to it to reflect the accuracy of the WGS 84 datum ensemble.

Even

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