[gdal-dev] GDAL 3.7.0 Proj 6.3.1 strange behavior when performing NAD83(EPSG:4152) to NAD83 HARN(EPSG:4269) realization transformation

[David Klaus]

Greg,

Thank you for that information. I'll put together some example code and
post that shortly.

As far as upgrading Proj4; because we build Proj4 statically in our custom
build, it's not a trivial task to upgrade versions. Also, I think there
might be compatibility reasons why we've stuck with 6.3.1 up until now.

But if NAD83 realization transformation functionality has been expanded and
improved in later versions, it might be worth it for us to upgrade. I was
wondering, judging by the contents of the proj-datumgrid packages I've
found online, it looks like Proj4 did not support any NAD83 realization
transformations besides 1986->HARN before at least Proj4 7.0.

Do you happen to know if this is true or not? I'm having trouble confirming
this online,

On Mon, Jul 15, 2024 at 11:06 AM Greg Troxel via gdal-dev <
gdal-dev at lists.osgeo.org> wrote:

> You didn't, as far as I can tell, post the code that is not doing what
> you want.  Or perhaps turn that code into a small test case program.
> People reading that would be able to be more helpful, and the code
> example could help others.
>
> Proj 6.3 is quite old.   I recommend you update to the latest release
> and the latest gridshift package before debugging further.   I am not a
> gdal or proj maintainer, but I am packager for both, and often rant
> about NAD83 and WGS84 issues.   In general, proj has a hard time dealing
> reasonably with WGS84 (which you aren't at the moment), and the
> transforms among the various NAD83 are complicated.  I am not the least
> bit sure they are all in the epsg dataset.
>
> You should very likely be using projinfo, and also thinking about how
> you are conveying the area of applicability when setting up the
> transform.
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>

-- 
David Klaus
Carlson Software

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