[Qgis-user] Changes from 3.18 to 3.20

[QGIS.USER]

Hi All,
	What has changed between 3.18 and 3.20 (64-bit running under W7 &
W10) that causes a project to 'lose' its CRS conversions?

I am UK based and only ever use OSGB 1936 / British National Grid
(EPSG:27700) as my CRS. I have a number of current projects that are fine in
3.18 with no errors or warnings.  I have installed 3.20.1 under W10 (in
tandem with 3.18). On opening the project I get a warning message "Used a
ballpark transform from EPSG:27700 to EPSG:4326". There is a more detailed
message:

An alternative, ballpark-only transform was used when transforming
coordinates between EPSG:27700 - OSGB36 / British National Grid and
EPSG:4326 - WGS 84. The results may not match those obtained by using the
preferred operation:

+proj=pipeline +step +inv +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717
+x_0=400000 +y_0=-100000 +ellps=airy +step +proj=hgridshift
+grids=OSTN15_NTv2_OSGBtoETRS.gsb +step +proj=unitconvert +xy_in=rad
+xy_out=deg

Possibly an incorrect choice of operation was made for transformations
between these reference systems. Check the Project Properties and ensure
that the selected transform operations are applicable over the whole extent
of the current project.
 
What do I need to do to prevent this warning message please?

Best,

Ray Carpenter


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