Re: [Talk-GB] West Mids Ward Boundaries
On 7 April 2010 12:08, Andy Robinson (blackadder-lists) < ajrli...@googlemail.com> wrote: > What I'm meaning by verification is interrogating the boundary line with > the > features already mapped on the ground. In many cases we know where the back > of gardens are for instance, or the position of a water course, railway > line > or a parish boundary. Many other boundaries, including Ward boundaries, tie > in with these features. So, for example, if a boundary actually follows a > stream and the stream is in OSM, then logically our boundary should follow > the stream, even if the OS have a slightly different alignment for the > feature. > > Oh right, yes, I'm with you now. It does need to be imported, but can be checked and in places brought into line with other features *with great care *. In my experience most ward boundaries go between streets, down the middle of a street, along a natural feature such as a stream, parallel to a railway line, or quite often they just jump across "empty" space following no particular feature. They also sometimes switch from going down the middle of a street to taking in both sides, which will again mean mappers will need to be very careful about changing them. Tom -- http://tom.acrewoods.net http://twitter.com/tom_chance ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] West Mids Ward Boundaries
Tom Chance [mailto:t...@acrewoods.net] wrote: >Sent: 07 April 2010 11:41 AM >To: Andy Robinson (blackadder-lists) >Cc: Ed Loach; Steve Doerr; talk-gb@openstreetmap.org >Subject: Re: [Talk-GB] West Mids Ward Boundaries > >On 7 April 2010 11:29, Andy Robinson (blackadder-lists) > wrote: > > > Its also worth noting how the OS maintains this boundary-line data. >Its not > apparently, as you might have thought, tied to OS MasterMap, which >you would > think would provide precise positioning based upon land ownership >etc. > Instead it's based off the 1:10k mapping, basically StreetView though >not > necessarily that style. So importing boundaries isn't necessarily a >good > idea and in any case is likely to conflict to some degree with >existing > data. That's why prefer a manual process. There are not that many >boundaries > to sort, so it's not like it would take years to do anyway. > > > The NaPTAN import has proved to me that we should never trust >imported data > without our own verification. > > > >That's interesting, thanks. But how do we verify ward boundaries if not >from the open OS data? > >The only other place you can go is your local authority, whose records are >polluted by non-free OS data. That or you extrapolate boundaries from the >electoral register, which lists every street in wards and (one further >level down) polling districts. That would require both the register in an >appropriate format (as a local party officer I have one for Southwark) and >the technical skills & time to do that (which I lack). I think maybe your second para actually answers the question. Wards are all about people and places, so on the whole one would expect that if a street is in a particular ward then the boundary would encompass at least all of the street, ie the boundary would not run down the middle of the back gardens. Just like with public footpaths it's the text description of the boundary (or what is within it) that appears to be more revealing than the line on the map alone. What I'm meaning by verification is interrogating the boundary line with the features already mapped on the ground. In many cases we know where the back of gardens are for instance, or the position of a water course, railway line or a parish boundary. Many other boundaries, including Ward boundaries, tie in with these features. So, for example, if a boundary actually follows a stream and the stream is in OSM, then logically our boundary should follow the stream, even if the OS have a slightly different alignment for the feature. > >I can't see any better option at the moment than an import from the open OS >data, whether StreetView or the future release of the vector stuff. The Boundary-line data set is vector, so I assume it will be the same product if its also released with VectorMap District. Not withstanding any changes of Boundary-Line in the proposed May update by the OS. Cheers Andy > >Best wishes, >Tom > > >-- >http://tom.acrewoods.net http://twitter.com/tom_chance > > >No virus found in this incoming message. >Checked by AVG - www.avg.com >Version: 9.0.791 / Virus Database: 271.1.1/2795 - Release Date: 04/06/10 >19:32:00 > ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] West Mids Ward Boundaries
When thinking about maintaining boundary imports, there is a further complication in that many boundaries follow other features - that are already mapped with varying degrees of precision. I can see a case for handling boundaries differently since the OS boundary data is "definitive" - in the sense that it doesn't have a physical existence on the ground, and the OS has responsibility for maintaining it in future. But there are bound to be conflicts where a boundary follows a stream, or another physical feature that has been mapped from GPS, or other sources. Would there be some way of protecting imported boundary data, and subsequently importing updates - while allowing this data to be combined with other features that still need to be edited? ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] West Mids Ward Boundaries
On 7 April 2010 11:29, Andy Robinson (blackadder-lists) < ajrli...@googlemail.com> wrote: > Its also worth noting how the OS maintains this boundary-line data. Its not > apparently, as you might have thought, tied to OS MasterMap, which you > would > think would provide precise positioning based upon land ownership etc. > Instead it's based off the 1:10k mapping, basically StreetView though not > necessarily that style. So importing boundaries isn't necessarily a good > idea and in any case is likely to conflict to some degree with existing > data. That's why prefer a manual process. There are not that many > boundaries > to sort, so it's not like it would take years to do anyway. > The NaPTAN import has proved to me that we should never trust imported data > without our own verification. > That's interesting, thanks. But how do we verify ward boundaries if not from the open OS data? The only other place you can go is your local authority, whose records are polluted by non-free OS data. That or you extrapolate boundaries from the electoral register, which lists every street in wards and (one further level down) polling districts. That would require both the register in an appropriate format (as a local party officer I have one for Southwark) and the technical skills & time to do that (which I lack). I can't see any better option at the moment than an import from the open OS data, whether StreetView or the future release of the vector stuff. Best wishes, Tom -- http://tom.acrewoods.net http://twitter.com/tom_chance ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] West Mids Ward Boundaries
Ed Loach wrote: >Sent: 07 April 2010 11:01 AM >To: 'Steve Doerr'; talk-gb@openstreetmap.org >Subject: Re: [Talk-GB] West Mids Ward Boundaries > >Steve wrote: > >> I'd prefer to see boundaries handled by an automated (and >nationwide) >> import process, as the OS data is likely to be at least as good as > >> contributors' own efforts and usually much better AND they are >committed >> to maintaining it going forward. Which seems a good opportunity to >mention >> that those of you working on the technical aspects of using the OS >data >> need to have a thought to how future updates will be handled. It's >much >> easier to insert a load of brand new data than to update existing >data >> from a refreshed set of source data in the future. You will have >to be >> able to distinguish new data to be inserted from existing data >that may >> have changed and existing data that may need deleting. Just a >thought. > >As I suspect there won't be any ward data currently in, the idea >sounds somewhat appealing, BUT I have not yet seen anywhere where >imported boundaries have been done well and have spent many an hour >tidying up the results (recently in Haiti and ongoing in GA, USA). >Examples include adjacent areas using overlapping ways rather than a >single shared way, an admin boundary being imported as a single way >which then needs splitting (and any duplicate ways de-duplicating) >before a relation can be created, and so on. If such an import were >to be done, it should be done well or not at all. > Its also worth noting how the OS maintains this boundary-line data. Its not apparently, as you might have thought, tied to OS MasterMap, which you would think would provide precise positioning based upon land ownership etc. Instead it's based off the 1:10k mapping, basically StreetView though not necessarily that style. So importing boundaries isn't necessarily a good idea and in any case is likely to conflict to some degree with existing data. That's why prefer a manual process. There are not that many boundaries to sort, so it's not like it would take years to do anyway. The NaPTAN import has proved to me that we should never trust imported data without our own verification. Cheers Andy ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] West Mids Ward Boundaries
Steve wrote: > I'd prefer to see boundaries handled by an automated (and nationwide) > import process, as the OS data is likely to be at least as good as > contributors' own efforts and usually much better AND they are committed > to maintaining it going forward. Which seems a good opportunity to mention > that those of you working on the technical aspects of using the OS data > need to have a thought to how future updates will be handled. It's much > easier to insert a load of brand new data than to update existing data > from a refreshed set of source data in the future. You will have to be > able to distinguish new data to be inserted from existing data that may > have changed and existing data that may need deleting. Just a thought. As I suspect there won't be any ward data currently in, the idea sounds somewhat appealing, BUT I have not yet seen anywhere where imported boundaries have been done well and have spent many an hour tidying up the results (recently in Haiti and ongoing in GA, USA). Examples include adjacent areas using overlapping ways rather than a single shared way, an admin boundary being imported as a single way which then needs splitting (and any duplicate ways de-duplicating) before a relation can be created, and so on. If such an import were to be done, it should be done well or not at all. Ed ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] West Mids Ward Boundaries
I'd prefer to see boundaries handled by an automated (and nationwide) import process, as the OS data is likely to be at least as good as contributors' own efforts and usually much better AND they are committed to maintaining it going forward. Which seems a good opportunity to mention that those of you working on the technical aspects of using the OS data need to have a thought to how future updates will be handled. It's much easier to insert a load of brand new data than to update existing data from a refreshed set of source data in the future. You will have to be able to distinguish new data to be inserted from existing data that may have changed and existing data that may need deleting. Just a thought. Steve From: Tom Chance Sent: Wednesday, April 07, 2010 9:35 AM To: talk-gb@openstreetmap.org Subject: Re: [Talk-GB] West Mids Ward Boundaries On 7 April 2010 09:10, Andy Robinson (blackadder-lists) wrote With the election process underway we might think about a topical map. If we can get the ward boundary data into OSM in time then we could show a map with some colouring that shows what the current lay of the land is in the west mids and which are marginal seats, retiring candidates, etc etc. I think this would be really good. As somebody pretty involved in local politics (and running to win a council seat) I'm really looking forward to gettign the full administrative boundaries into OSM. Wards where more than one party are represented will be an interesting challenge if you want to colour them, as will areas with quite a diverse set of parties with similar traditional colours and with independents. One fly in the ointment is that the ward boundaries in Boundary-Line are I believe the 2009 positions and not the new ward boundaries that will shape this next election. The changes are discussed in the User Guide (Annexe A). I assume that OS OpenData Boundary Line will be updated to the new boundary data in May, but I don’t see anything specific on that yet At least in my area the ward boundaries are unchanged, though a few Parliamentary constituencies have changed :-) Tom -- http://tom.acrewoods.net http://twitter.com/tom_chance ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] West Mids Ward Boundaries
On 7 April 2010 09:10, Andy Robinson (blackadder-lists) < ajrli...@googlemail.com> wrote > > With the election process underway we might think about a topical map. If > we can get the ward boundary data into OSM in time then we could show a map > with some colouring that shows what the current lay of the land is in the > west mids and which are marginal seats, retiring candidates, etc etc. > I think this would be really good. As somebody pretty involved in local politics (and running to win a council seat) I'm really looking forward to gettign the full administrative boundaries into OSM. Wards where more than one party are represented will be an interesting challenge if you want to colour them, as will areas with quite a diverse set of parties with similar traditional colours and with independents. > One fly in the ointment is that the ward boundaries in Boundary-Line are I > believe the 2009 positions and not the new ward boundaries that will shape > this next election. The changes are discussed in the User Guide (Annexe A). > I assume that OS OpenData Boundary Line will be updated to the new boundary > data in May, but I don’t see anything specific on that yet > At least in my area the ward boundaries are unchanged, though a few Parliamentary constituencies have changed :-) Tom -- http://tom.acrewoods.net http://twitter.com/tom_chance ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
