[PROJ] Implementation of NADCON5 transformations for USA

[Howard Butler]

> On Dec 16, 2022, at 8:03 AM, Greg Troxel <gdt at lexort.com> wrote:
> 
> 
> Even Rouault <even.rouault at spatialys.com> writes:
> 
>> 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...
> 
> Wow, this is amazing to see.   I think it is definitely for the good!

Thank you so much to whomever sponsored this work. This has been a really important missing workflow piece for US-based activities.

Howard