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The data I work with requires me to project between WGS84 (4326) and OSGB (27700), the default projection in PostGIS is using the older less accurate version of the projection.

I am trying to add both the OSTN02 and OSTN15 projections and have successfully added the .gsb files into

C:\Program Files\PostgreSQL\9.6\share\contrib\postgis-2.4\proj

and used

INSERT INTO "spatial_ref_sys" ("srid","auth_name","auth_srid","srtext","proj4text") VALUES (27715,'EPSG',27700,'PROJCS["OSGB 1936 / British National Grid",GEOGCS["OSGB 1936",DATUM["OSGB_1936",SPHEROID["Airy 1830",6377563.396,299.3249646,AUTHORITY["EPSG","7001"]],AUTHORITY["EPSG","6277"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4277"]],UNIT["metre",1,AUTHORITY["EPSG","9001"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",49],PARAMETER["central_meridian",-2],PARAMETER["scale_factor",0.9996012717],PARAMETER["false_easting",400000],PARAMETER["false_northing",-100000],AUTHORITY["EPSG","27700"],AXIS["Easting",EAST],AXIS["Northing",NORTH]]','+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +ellps=airy +units=m +no_defs +nadgrids=OSTN15_NTv2_OSGBtoETRS.gsb ');

to create the new entry in the spatial_ref_sys table with a custom 'srid' number.

All of this works fine and I can see the difference in projections in QGIS.

However what I would like to do is have these projections available as default on new PostGIS extended databases? I tried entering the projects into the spatial_ref_sys.sql file but this doesn't seem to make a difference? Is there a way to do this?

  • After additional research on coordinate systems, QGIS and PROJ, it seems that this topic is a little more tricky when it comes to projections like the one I listed in the question. The newer version of PROJ (5.0) may help with my problem, but it may require other software to update before it solves my issue. – Andy Dixon Apr 4 '18 at 16:00
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You could create a new extension

https://www.postgresql.org/docs/9.1/static/extend-extensions.html

that extend the database with postgis and then add your custom projections.

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