Sorry, but to me there's a more important question than the exact position on the ground.
Are we allowed to use their data? I thought a lot of OS stuff was covered by © that isn't licensed? Thanks Graeme On Thu, 11 Jun 2026 at 03:09, Graham Whaley <[email protected]> wrote: > On 10 Jun 2026, at 17:07, David Woolley <[email protected]> > wrote: > > > On 09/06/2026 16:01, Graham Whaley wrote: > > The OS trig data says (iirc) that it should still be accurate to 0.1m > > > It shouldn't be! Continental drift should have changed it by almost > double that. Even the longitude of Greenwich varies relative to WGS 84, > over time, and latitude also does. GPS uses the WGS 84 reference frame, > not the ETSR89 one, which is specific to the Eurasian tectonic plate, so is > gives more stable coordinates in past and present parts of Europe. > > The national grid references should be stable, but OSM is GPS based, not > NGR based. > > (It is possible that some high precision GPS receivers return coordinates > that are corrected for this, but I don't think those are true GPS > coordinates.) > > > Heh, indeed. Not long after posting that I was reading about OSM, WGS84 > and continental drift… all a bit beyond my current comprehension, but, I’d > like to do the right/best thing we can with the OS trigpoint data… if > anybody would like to review and chip in ? > I was actually reading up a bit as I want to work out if I need to apply a > decimal place ‘filter’ to some of the co-ordinates, as I think a bunch of > them have ended up as doubles that are not really showing an honest > representation of the underlying data iyswim. > > The OS data description can be found at: > > > https://www.ordnancesurvey.co.uk/geodesy-positioning/legacy-data/trig-search > > and the passage I was thinking of says (but, I think really needs to be > read in context on that page…) > > “ > The archive coordinates supplied for these triangulation stations have not > been > realised via ETRS89 and OSTN15. They are the original archive coordinates > and can therefore no longer be considered as true OSGB36 National Grid > Coordinates of the station. It is expected that agreement between > ETRS89/OSTN15 derived coordinates and the original archive coordinates of > triangulation stations (down to third order) will be at the 0.10 metre root > mean square (r.m.s) level. > “ > > (side note - I’ve just identified a bug that is spitting out FB numbers in > the reviewnodes.osc file that are not matching what I expect - will work on > finding/fixing that. Just posting here in case somebody happens to be > running the code. I’ll probably start using github Issues to track such > things from now on). > > Graham > > _______________________________________________ > Talk-GB mailing list > [email protected] > https://lists.openstreetmap.org/listinfo/talk-gb >
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