[PROJ] Implementation of NADCON5 transformations for USA

[Even Rouault]

Hi,

I just wanted to point to https://github.com/OSGeo/PROJ/pull/3510 which 
implements the NADCON5 transformations, with a corresponding pull 
request to PROJ-data to add  the grids as GeoTIFF files, for USA 
geodetic datums NAD27 --> NAD83(86) --> NAD83(HARN) --> NAD83(FBN) --> 
NAD83(NSRS2007) --> NAD83(2011). We can now reproduce exactly the 
results of NGS tools, such as NCAT and their online REST API.

This means that the transformations within the NAD83 family which used 
to be mostly null transformations (except NAD83(86)->NAD83(HARN) where 
we currently use the HPGN grids) are no longer null. This might change 
results in your workflows once this is merged, but this is hopefully for 
the good...

Even

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