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#1 2018-05-09 15:25:28

lefty74
Member
From: Peckham, London, GB
Registered: 2014-06-01
Posts: 7

London Borough of Southwark ward boundaries revised

We just had an election in Southwark and the ward boundaries have been revised.
Official info here:
https://www.southwark.gov.uk/council-an … -southwark
http://www.lgbce.org.uk/all-reviews/gre … /southwark

I am interested in updating OSM, but would like advice:

Is there someone who tries to curate political boundaries in Southwark?

The boundaries are published, in fact they have to be due to freedom of information. They are published on top of an OS map that is crown copyright. If I just use the map as reference to transfer the boundary information, without transferring information from the base OS map, is that legal? It would seem to be fair use to me.
Published map here: https://www.lgbce.org.uk/__data/assets/ … ht1_SO.pdf

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#2 2018-05-09 22:39:01

SK53
Member
Registered: 2009-01-11
Posts: 360

Re: London Borough of Southwark ward boundaries revised

I doubt if anyone is checking ward boundaries in a systematic way.

The data you mention is not suitable for OSM. However, the Ordnance Survey does publish boundary data as Open Data (usually updated twice a year), and this has been the usual source for ward boundaries for the past 8 years. As boundaries are usually stored as relations they may need a bit of care editing them if you are unfamiliar with them

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#3 2018-05-10 01:12:44

lefty74
Member
From: Peckham, London, GB
Registered: 2014-06-01
Posts: 7

Re: London Borough of Southwark ward boundaries revised

Thanks for your answer. I've reviewed the docs on boundary relations, so I'm OK with those. Can you help me understand how to figure out which public maps are suitable for OSM? I outlined my thinking in my OP that the base map is copyright to OS, but the boundary lines are drawn separately over the top of it and are a matter of public record. Does the copyright of the base map extend to the overlay too?

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#4 2018-05-10 10:37:30

SK53
Member
Registered: 2009-01-11
Posts: 360

Re: London Borough of Southwark ward boundaries revised

The problem is that nearly every 'public' map in Great Britain will have been created from Ordnance Survey data which remains copyright. Therefore we can only use two types of maps/data:

* Old maps which are out-of-copyright. Some are present in the editing tools. OSM also has a large collection online at: ooc.openstreetmap.org.
* Open Data published under various versions of the Open Government Licence (OGL). In the main the most useful collection is that under the OS Open Data banner, which includes Boundary Line. Be cautious with other datasets because although the data is notionally open, the actual geometries are not because they are derived from OS Master Map (the Land Registry Inspire Land Parcels data was a particularly vexed example). Footpath data issued by local authorities is probably OK.

When updating the relations you do need to take care not to damage other relations which use the same ways (for instance a London Borough boundary will be shared with the boundary of the adjacent borough and wards on both sides).

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#5 2018-06-20 10:55:27

lefty74
Member
From: Peckham, London, GB
Registered: 2014-06-01
Posts: 7

Re: London Borough of Southwark ward boundaries revised

FAO SK53 and anyone else who is interested, I have downloaded the OS OpenData Borderline set. It includes the updated Southwark wards, which were made law in 2016. The revisions involved not just moving boundaries but combining and renaming wards, so they are major changes that I think are worth updating in OSM. Here's my plan. I believe it won't cause any problems but would welcome feedback.

  1. Load shapefiles into JOSM for wards, boroughs and Westminster constituencies in Southwark and bordering Southwark

  2. Split ways at every intersection of ward, borough or constituency

  3. Create relations for each ward, borough and constituency

  4. Add each split way as members of every relation that it borders

  5. Merge new ways with OSM data

  6. Delete old ways that are duplicated by the new ones

  7. Delete relations that are completely defined by new ways

  8. For relations that are only partially covered by the new ways, add the new ways to the existing relations, delete the new relations, and join the ends of the new ways to existing ones

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