Just to be clear though Colin, in that particular instance when I said the position of the railway line looked rather dodgy, that was when comparing a high degree of congruence between Cadastral Parcels and the satellite imagery (roads and buildings) and the adjacent railway lines cutting through them being out by so much that the railway line as currently shown in OSM would have been going through people's houses! (The houses weren't currently drawn in on OSM, just marked as a 'residential area'. I didn't import OS open data of the ward boundary, as it was sufficient to refer to the Boundary Commission and Lambeth's Council's published maps (the latter of which uses OSM!). About 90% of the ward boundary in questoon is just defined as 'down the middle of the road' or 'along the railway line' .... a few bits were 'along the fence between two back gardens' (which the Casastral Parcels helps a lot to sanity check)
On Mon, 21 Feb 2022, 21:49 Colin Smale, <colin.sm...@xs4all.nl> wrote: > If the position of the boundary is imported from a source that ultimately > has a very high precision, for example Ordnance Survey or a Council's GIS > system through a shapefile or similar, then the location as recorded in OSM > will likely be more accurate than what would be obtained from tracing from > aerial photos. In other words, if a boundary and a road/railway/etc > *almost* coincide, more consideration should be given to moving the road to > match the imported boundary than the other way around. > > Having said that, the exact line of a boundary tends to get frozen at the > moment the Order is made, even if the road/railway/etc is subsequently > realigned. I strongly recommend that boundaries and other features do *not* > get combined or even share nodes, unless it can be demonstrated that the > link between them is dynamic, i.e. a change to one necessarily means a > change to the other. > > On 02/17/2022 3:41 PM David Davis via Talk-gb-london < > talk-gb-london@openstreetmap.org> wrote: > > > > Yeah Tom, > this is conclusion I reached too: > if a ward boundary is legally defined as being a particular geographical > feature (e.g. centre line of a road) then it is better to have that way on > OSM tagged with a relation (even if its position is a metre or two off > perfect) rather than have another line imported and tagged as the boundary. > And probably even worse: if the road *is* in precisely the right position, > neither is it helpful to have another imported line superimposed right on > top of it, as it makes it very fiddly to try and edit them subsequently. > So, slightly timeconsuming as it is, I think it's probably best to set > them up manually. > > On Thu, Feb 17, 2022 at 1:55 PM Tom Chance <t...@acrewoods.net> wrote: > > I've previously found it valuable to have the ward boundaries in OSM, and > am responsible for all the Southwark (not Lambeth) ward boundaries, plus a > few Lambeth, Croydon and Bromley. Sometimes the misalignment of open data > and OSM data can lead to mistakes. It's not a big deal if they aren't in, > but I don't see any reason to say they *shouldn't* be. > > If you're going to update them (great!) I think they work better as > relations using - where relevant - existing objects like roads where they > go down the middle of a road. Otherwise, again, things can get misaligned > and otherwise go wrong. So a straight import isn't as good an option as the > rather more painstaking manual approach. > > Tom > > m: 07866 447 075 > w: http://tomchance.org > > > On Wed, 16 Feb 2022 at 11:46, Russ Garrett <r...@garrett.co.uk> wrote: > > My controversial opinion is that these shouldn't be in OSM. > > The definitive boundaries are freely available as open data in OS > Boundary Line (although they won't usually appear there until after > the boundaries take effect). The current UK-wide coverage of ward > boundaries in OSM is pretty minimal, although it looks like most of > the old Lambeth wards are in OSM: > > > http://overpass-turbo.eu/?q=W291dDpqc29uXVt0aW1lxIHEgzI1XTsKKAogIG53clsiYsSBbmRhcnkiPSJwb2xpxItjYWwixInEqMSqxKxpxK5sX2RpdmlzacSHxKYid8SjZMSxKHt7YsSfeH19KcSUxY8KxI8gxJ9kecSUPsSUxZNza2VsIHF0Ow&c=BJp6-ioHTL > > As someone who uses this boundary data relatively frequently, there's > no reason why I should use OSM when the data is incomplete, and > boundaries in OSM may have been altered (accidentally or otherwise). > They're not surveyable, the data is freely available elsewhere - I > don't see why it's worth spending our time making sure it's replicated > in OSM. > > Cheers, > > Russ > > On Wed, 16 Feb 2022 at 11:27, David Davis via Talk-gb-london > <talk-gb-london@openstreetmap.org> wrote: > > > > Hello, > > a complete revamp of the electoral wards in Lambeth borough comes into > effect in May 2022, with 25 new wards. > > (See > https://love.lambeth.gov.uk/a-new-political-map-for-the-2022-lambeth-borough-council-elections/ > for info). > > > > I'm guessing the boundaries are available as open data, > > and some bright spark on this list will know how to import it into OSM > in a hugely more efficient way that me trying to manually draw and tag the > new boundaries...? > > (Amusingly, on the map on Lambeth Council's page about it, someone > literally has just drawn the boundaries by hand on top of a screengrab from > OSM!) > > > > Anyone interested this task? > > > > (A few of the existing Lambeth wards were tagged on OSM already, but the > majority actually weren't. But every existing ward boundary is changing in > any case...) > > _______________________________________________ > > Talk-gb-london mailing list > > Talk-gb-london@openstreetmap.org > > https://lists.openstreetmap.org/listinfo/talk-gb-london > > > > -- > Russ Garrett > r...@garrett.co.uk > > _______________________________________________ > Talk-gb-london mailing list > Talk-gb-london@openstreetmap.org > https://lists.openstreetmap.org/listinfo/talk-gb-london > > _______________________________________________ > Talk-gb-london mailing list > Talk-gb-london@openstreetmap.org > https://lists.openstreetmap.org/listinfo/talk-gb-london > >
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