[PROJ] proj8 and NAD27 <-> NAD83 transform

[Even Rouault]

Kirk,

the relationship between a transformation and its area of use is now 
done through an entry in the usage table.

See 
https://github.com/OSGeo/PROJ/blob/dcc2a94eb1c5eda5ede6275b58ae5873e78bb9c0/data/sql/helmert_transformation.sql#L2244

Even

Le 03/06/2021 à 22:03, Kirk Waters - NOAA Federal a écrit :
> Even,
> I decided to script out adding the transforms to the proj.db file so I 
> can automatically have my system add them when new proj.db files get 
> released. One thing I haven't figured out is how the extent is 
> associated with the transform. For 8971, I don't see anything in the 
> helmert_transformation table that looks close except the 'IOGP-Usa 
> GoM' for the operation version. EPSG.org shows the extent code for 
> transform 8971 is 3357, which matches what I find in the extent table, 
> but I don't see where in proj.db that's happening. The name for extent 
> 3357 is 'USA - GoM OCS', so it doesn't match the 
> helmert_transformation entry for 8971. Apologies if I'm asking 
> something that's clearly laid out. I just haven't found the right docs 
> yet.
>
> Kirk
>
>
> On Thu, Jun 3, 2021 at 6:49 AM Even Rouault 
> <even.rouault at spatialys.com <mailto:even.rouault at spatialys.com>> wrote:
>
>
>     Le 03/06/2021 à 12:37, Kirk Waters - NOAA Federal a écrit :
>     > Even,
>     > Thank you very much, that's very helpful. It's along the lines
>     of what
>     > I was thinking was the problem, but I hadn't gotten far enough to
>     > realize I could add an entry in the database. The other option
>     is to
>     > figure out the right EPSG code to pass to GDAL to pretend the
>     > transform has already happened.
>
>     If you use gdalwarp, you can lie a bit and set -s_srs EPSG:2273 to
>     force
>     "NAD83 / South Carolina (ft)" as the source CRS, and then you'll
>     get the
>     transformation to NAD27 using the CONUS grid.
>
>     Even
>
>
>     -- 
>     http://www.spatialys.com <http://www.spatialys.com>
>     My software is free, but my time generally not.
>
-- 
http://www.spatialys.com
My software is free, but my time generally not.

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