[PROJ] Obtaining possible transformation pipelines

[Even Rouault]

> If I have a proj string representing a coordinate operation, is there
> any way to determine what grids are required for using it when those
> grids are NOT available for use on the system?

I don't think so. As you find out, PROJ will refuse to instanciate a 
coordinate operation from a PROJ string that has a grids not present on the 
system.

Asthere are not so many ways of expressing grids in PROJ grids, basically you 
could look for +grids=xxxxx

Even

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