Hi Jim, Here is a full article on how projections (specifically the British National Grid) work in QGIS and what you can do to improve your data collection when using on-the-fly transformation: https://merginmaps.com/docs/gis/projections/#projections
Kind regards Saber On Fri, 1 May 2026 at 19:36, Jim Jackson via QGIS-User < [email protected]> wrote: > > > QGIS version 3.40.6-Bratislava > QGIS code branch Release 3.40 > OS Linux Devuan GNU/Linux 6 (excalibur) (basically Debian Trixie) > > Hi All, > > As a member of a community Archaeology Group, I'm using QGIS for recording > archaeological features in the UK. I'm using Google Satellite, > OpenStreetMap and National Library of Scotland historic basemaps, which > (as > I understand it) use EPSG:3857. > > I have an RTK GPS receiver for collecting data points which are in > EPSG:4326. > I > also get UK National Grid data points from a colleague who has access to a > total station. > > As I think I understand it, I need to set the project CRS to UK national > grid EPSG:27700 to get sensible distance measurements However I then get > occasional warnings "Used a ballpark transform from EPSG:27700 to > EPSG:3857" indicated less than accurate transformations, and then I get > lost!!!! > > Can anyone point me to a tutorial on how to set up QGIS in the UK to get > accurate transformations in these circumstances (which can't be that > unusual). > > Any advice and/or pointers where I've gone wrong gratefully received. > > Jim Jackson > > > _______________________________________________ > QGIS-User mailing list > [email protected] > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user > -- Saber Razmjooei Co-Founder lutraconsulting.co.uk [image: https://www.linkedin.com/in/saber-razmjooei/] <https://www.linkedin.com/in/saber-razmjooei/> <https://www.youtube.com/@LutraConsulting> <https://github.com/lutraconsulting> <https://www.lutraconsulting.co.uk/>
_______________________________________________ QGIS-User mailing list [email protected] List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
