[OSM-talk-ie] Estimate of number of building=* in Ireland

[Mateusz Konieczny]

both building=residential and landuse=residential
are valid tagging

(though, if possible then building=house
or other more specific value is preferable)


May 14, 2020, 12:47 by t4dc4n at gmail.com:

> The residential tag should be used for an area not a house.
>
> On Wed, 13 May 2020 at 14:38, Donie Kelly <donie.kelly at gmail.com> wrote:
>
>> Don’t buildings have tags? Did I see a residential tag? Is it used in all
>> cases?
>>
>> > On 13 May 2020, at 13:24, Colm Moore <colmmoore72 at hotmail.com> wrote:
>> >
>> > Hi,
>> >
>> > Inspired by seeing the estimate in the Microgrant application of 5.5
>> million buildings on the island of Ireland, I did some number crunching.
>> >
>> > I downloaded the populations of Kilkenny townlands (1,500+) from the CSO
>> and analysed the population against the number of buildings per civil
>> parish (100+) for County Kilkenny. This is assuming Kilkenny has all or
>> nearly all buildings mapped. Based on my inspections, this is largely true.
>> >
>> > The CSO data is somewhat distorted for the Kilkenny city area (100+
>> townlands), due to the way the CSO have arranged the townlands and civil
>> parishes. I could look at this in more detail, but there would be a few
>> hours of effort (unless someone has a simple way of calculating number of
>> buildings per area, for a large number of areas).
>> >
>> > I calculated the 'number of buildings per civil parish' using the
>> Overpass Turbo query [building=* in "civilparishname, Kilkenny"]. Overpass
>> Turbo gives a summary of the data in the bottom right corner of the screen,
>> e.g.
>> >
>> > Loaded – nodes: 4261, ways: 867, relations: 2
>> > Displayed – pois: 0, lines: 0, polygons: 866
>> >
>> > I took the number of polygons to mean the number of buildings (this
>> might not be perfect - I don't know how those numbers add up).
>> Additionally, some polygons, e.g. building=terrace represent several
>> buildings, while in other cases buildings may have been crudely split or
>> joined-up.
>> >
>> > Depending on the civil parish, we're looking at 0.32-2.29 polygons per
>> capita (0.44-3.15 people per building). Rural areas ten to have more
>> polygons per capita, especially due to farm outbuildings, while urban areas
>> have fewer polygons per capita, due to apartments buildings and
>> semi-detached buildings (e.g. two square houses joined together might have
>> only six nodes).
>> >
>> > I also calculated 4.40-5.83 nodes per polygon. This means some civil
>> parishes have predominantly rectangular polygons / buildings, whereas
>> others have many L-shaped or other-shaped polygons / buildings.
>> >
>> > As I wasn't able to immediately get some 'number of buildings per civil
>> parish' numbers (Overpass Turbo had problems returning them, possibly due
>> to duplicate names and variations in name spellings), I had to calculate
>> them from their component townlands, using the Overpass Turbo query
>> [building=* in "townlandname, civilparishname, Kilkenny"].
>> >
>> > Depending on the townland, we're looking at 0.23-8.00 polygons per
>> capita (0.13-4.37 people per building) and 3.91-6.45 nodes per polygon
>> (i.e. some townlands have large numbers of semi-detached or terraced
>> buildings, whereas others have a high number of complicated-shape polygons
>> / buildings or buildings with too many mapped nodes). It is usual to see
>> more extreme spreads when looking at smaller areas.
>> >
>> > I'm coming up with about 5.4 million (close enough!) buildings for the
>> whole island, assuming the pattern is the same everywhere. However, as
>> shown by analysing the smaller areas, there is variation and the 'final'
>> number will vary from that. Of course, given that OSM is an ongoing
>> project, there will never be a final number.
>> >
>> > Colm
>> > VictorIE
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