This seems to be a repeat of previous CRS errors in QGIS 3.10+
New install of QGIS 3.10.5-A Coruña LTR on clean install of Linux Xubuntu 20.04 (install from Ubuntu-LTR PPA and apt). This OS install accesses the /home folder from a previous Xubuntu 18.04 install.
To create the error/problem:
Start a new project, QGIS defaults to EPSG:4326. No error messages.
Change project CRS to EPSG:27700 (British Ordnance Survey) and a warning message appears:
Used a ballpark transform from EPSG:27700 to EPSG:4326
The same error occurs if I use EPSG:7405 (also British Ordnance Survey). Selecting random CRSs or custom CRSs does not produce an error message: the error appears to be unique to British Ordnance Survey projects.
- Clicking on the error message Details gives:
An alternative, ballpark-only transform was used when transforming coordinates between EPSG:27700 - OSGB 1936 / British National Grid and EPSG:4326 - WGS 84. The results may not match those obtained by using the preferred operation:
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.
The project properties correctly state EPSG:27700. Moreover, this error occurs on a blank/empty project, therefore there have been no transformations attempted or performed.
- Creating a template file set to EPSG:27700 and starting a new project from the template file produces the same error.
No other solution(s) suggested.
Question: What is the practical effect of this error? I need to work to as high a level of accuracy as possible and certainly to better (less than) than 5m error. Do I need to worry about the error or not? Can I resolve the error?
QGIS version 3.10.5-A Coruña
QGIS code revision 984615fe1e
Compiled against Qt 5.12.8
Running against Qt 5.12.8
Compiled against GDAL/OGR 3.0.4
Running against GDAL/OGR 3.0.4
Compiled against GEOS 3.8.0-CAPI-1.13.1
Running against GEOS 3.8.0-CAPI-1.13.1
Compiled against SQLite 3.31.1
Running against SQLite 3.31.1
PostgreSQL Client Version 12.2 (Ubuntu 12.2-4)
SpatiaLite Version 4.3.0a
QWT Version 6.1.4
QScintilla2 Version 2.11.2
Compiled against PROJ 6.3.1
Running against PROJ Rel. 6.3.1, February 10th, 2020
OS Version Ubuntu 20.04 LTS
Active python plugins mmqgis; LAStools; GeoCoding; quick_map_services; processing; db_manager