[postgis-users] Help shaping the future: how do your use of spatial_ref_sys ?

Robert Coup robert.coup at koordinates.com
Wed Feb 9 05:28:13 PST 2022

Hi Sandro,

On Fri, 4 Feb 2022 at 17:05, Sandro Santilli <strk at kbt.io> wrote:

> The question I have for you is: do you keep your custom CRSs
> in the spatial_ref_sys table ? If so:


>   - How many ?

A dozen or so. We use 800xxx numbering for no particular reason, but we try
and avoid exposing that.

>   - Do you also keep the entries installed by spatial_ref_sys.sql ?


>   - Do you ever update the table with entries from newer
>     spatial_ref_sys.sql ?

Yes. We keep postgis' spatial_ref_sys synchronised with the Proj DB version
we're running as best we can to make life simpler.

If we're moving things:

1. is spatial_ref_sys redundant for anything non-custom? Proj has a full
database now, why does PostGIS need it's own?
2. proj4text should disappear altogether too. If people have existing
proj4text they want to use... `projinfo -o WKT2:2019 '{my-proj4text}'`
3. Since CUSTOM:4326 and EPSG:4326 clash - the PK is the number; and
SRID-is-integer is part of SF-SQL (ie: that's not going to change anytime
soon) could we at least help people put their custom CRS in the right
place? Is there a defined custom number range we could use to initialise a

I think since Proj has gotten a lot smarter since v4, PostGIS should tend
towards helping people use it (supporting pipelines, using it's
DB/transform grids/etc) rather than adding additional abstractions over the


Rob :-)
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