[postgis-devel] PostGIS and the new Proj4 transformation pipeline

[G. Allegri]

Hi,
during the past days there's been a very interesting discussion within the
QGIS community [1] about the refactoring of its way of managing CRS
transformations. Some from Proj4 have joined the conversation to help in
understanding the newcoming Proj4 feature: transformation pipeline [2] [3].

This is a great and deep enhancement to the capabilities of Proj4, toward
more complex transformations and, consequently, higher precisions.

The new concept has lead to a new API and a new way to manage
transformations definitions.

I cross post it here because I find that this should be considered by
PostGIS too.
Just for a use case I recently was asked support for: employing grid shifts
within PostGIS. It's already possible to define a custom CRS with a
nadgrids parameter, but this suffers WGS84 pivoting, which is the current
way Proj4 works.
With the new pipeline it can be circumvente if a specific, straight, CRS to
CRS transformation is defined.

I hope there will be some interest here to keep this conversation going on,
looking at adopting the new Proj4 API in the future versions of PostGIS.

All the best,
Giovanni

[1] https://github.com/qgis/QGIS-Enhancement-Proposals/issues/100
[2] https://lnkd.in/emzw2HA
[3] https://kbevers.github.io/usage/transformation.html
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