In our app we are using several CRS - one of them is a custom one. I'd like to turn it into a proper CRS that PostGIS can fully support (e.g. administering valid transformations on it with something like ST_Transform, etc)
How would one do that?
I couldn't find any reference on this online. I found one for Oracle here - seems to be very detailed, transparent and straightforward process. What would be an alternative of this process in case of PostGIS?
Just add a row to the spatial_ref_sys table.
The most important column is proj4text, which describes the projection for the PROJ library. (Despite the name, the latest PostGIS uses the latest version of PROJ.)
I do not know if the srtext value is actually necessary, but you should be able to create it with gdalsrsinfo.
Also see Managing custom projections and Would it be worthwhile to use the PostGIS extension for custom planets?
proj4text would be enough?
The use of PROJ strings to describe a CRS is considered as legacy (one of the main weakness of PROJ strings is their inability to describe a geodetic datum, other than the few ones hardcoded in the +datum parameter), here: proj.org/development/quickstart.html So maybe srtext is actually preferrable.
spatial_ref_systable, but is already defined somewhere else (on spatialreference.org perhaps?). That's not what I'm looking for. I have totally made up coordinate system and want to properly add it tospatial_ref_sys.