Hello; Ive noticed a difference between the results returned by st_transform between Postgis 2.3 and Postgis 3.0 and wonder if anyone on this list might be able to explain why that is so.
I have a home rolled entry in the spatial_ref_sys table for a SRID called 927700. This is the UK Ordnance Survey coordinate system using OSTN02. The spatial_ref_sys.proj4text for this is (newline added for readability) '+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +ellps=airy +units=m +no_defs +nadgrids=OSTN02_NTv2.gsb' So it is using a gsb data file. The following query shows a difference converting a point in 4326 'WGS 84' to 927700 "OSGB 1936 / British National Grid" SELECT st_asewkt(st_transform(geomfromEWKT( 'SRID=4326;POINT(-0.077731 54.116851 86.778)' ), 927700)) AS a; postgres / postgis result 9.6 / 2.3 SRID=927700;POINT(525745.680454343 470703.162768111 86.778) 9.6 / 3.0 SRID=927700;POINT(525744.779056573 470705.423178893 86.778) A difference of -0.901 2.26 which is quite significant given that OSGB is measured in meters. Any ideas what is going on? David McKelvie _______________________________________________ postgis-users mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/postgis-users
