Areas union of smaller areas without needing shapes

[dracos]

It would be useful to have a way of having areas in the database that didn't have any associated shapes, because they are simply made up of other shapes unioned together. That way, more expensive P-in-P tests are unnecessary to discover the larger shapes, as they can simply be inferred from the smaller ones.

To do this, it would presumably need a table that links an area with the areas that make it up (similar to an area's children currently), and then anything that queries the database to return areas by postcode/point etc. adds the corresponding areas if needed.

This would mean technically e.g. the county councils could be dropped from the UK mapit and could be inferred simply from the district council. Probably not worth doing that precise case, but if things appear that are just groups of councils (e.g. road authorities in Norway), this could be worthwhile.

[RichardTaylor]

Police force areas tend to be defined as groups of council areas.

Making the boundaries of police force areas available might be valuable in advance of proposed elections for Police and Crime Commissioners.

[robinhouston]

Counties!

[dracos]

Just had a thought - if Area and Geometry were linked by a many-many relationship rather than one-many, then that would provide the functionality needed for this, and without having areas in Area without associated shapes. You could simply have Geometrys associated with more than one Area (so, conceivably, a ward geometry in Birmingham could be associated with the ward Area, the council Area, the West Midlands police Area, and those parent Areas wouldn't need their own larger geometries). Again, not worth doing for things in Boundary-Line, but this would probably be nicest way of doing police force areas and other things like that, no need for a new db table.

[dracos]

Request for #235 would be served by this also.

[symroe]

The Cambridge and Peterborough Devolution Deal creates a new administrative area made up of:

• Peterborough City Council
• Cambridgeshire County Council
• Fenland District Council
• Huntingdonshire District Council
• East Cambridgeshire District Council
• South Cambridgeshire District Council
• Cambridge City Council

https://www.cambridgeshire.gov.uk/devolution

A political post will be attached to this group, and I think that's a reasonable test for it being in Mapit.

I don't know if this will get it's own boundary in BoundaryLine, but this suggested model would be an excellent solution regardless.