I think you are on the right track, Andrew. Australian Bureau of Statistics (ABS) is a credible and independent statistical authority that we are lucky to have in this country. I would be confident of their data and analyses. Their Urban Centres and Localities (UCLs) looks suitable for our purpose. Your suggested population sizes to classified as cities, towns etc seem reasonable to me, but others may have different suggestions. However, I am not sure that we have clarified if OSM has permission to use current ABS data.
On Wed, 11 Oct 2023, at 4:22 PM, Andrew Davidson wrote: > On 6/10/23 18:14, Little Maps wrote: >> Thanks Graeme, it’ll be great to hear what others think too. Cheers Ian > > The first thing to keep in mind is how concentrated the AU population > is. Sydney and Melbourne both have 20% of the population living in them. > If we add on Brisbane we reach the 50% mark, which means the majority of > people live in one of three cities. As a result there is not much to go > around for the rest. > > If we adopted 50,000 as the cutoff for a city we're going to more than > halve the number of currently mapped cities. 50,000 might work for the > US (and is also the value the UN has adopted for global comparisons) but > it's too big for AU. At the other end 15,000 is too small, we'd end up > creating an additional 25% of cities. > > I would suggest that we adopt the ABS's threshold of 20,000. This is the > population level at which they consider a settlement starts to have > "gravity" and pulls in surrounding urban areas. It used to be 30,000 > back in the early days of their methodology but I assume they think > people are more mobile so the "pull in" starts earlier now. 20,000 also > has the benefit of not changing the number of cities we have by much. 10 > currently mapped cities would become towns and 13 current towns would > become cities. > > For towns the US threshold of 10,000 is way too crazy high. There are > 1,000+ things currently mapped as towns. If we adopted 10,0000 this > would drop to 101. Even 5,000 would only get that to 198. > > I was thinking that we would just use the ABS's UCL list. This divides > settlements into urban centres and urban localities. If a settlement is > on the urban centres list and its population is over 20,000, then that's > a city, otherwise it would be a town. In effect this is a cutoff of > 1,000, which the ABS has used for more than 50 years suggesting that > it's getting relatively smaller over time. > > The urban localities would be villages (a lower cutoff of ~200) and > settlements not on the list hamlets. > > The bigger shifts are going to be in the towns and villages. The UCL has > (using the rules above): > > 72 cities > 657 towns > 1080 villages > > but we currently have 1,000+ towns and 1,800+ villages. It is hard to be > very precise, as these will include place nodes nested inside other > urban centres and localities. > > I looked at the ratio of CTVs from the US/CA/NZ on the assumption that > being new world settlements the ratios should be similar. The 9 towns > for each city in AU is similar to the others 7/9/8. What is different is > the ratio of villages to towns. AU is 1.6 the others 2.4/4.0/2.3, which > suggests: > > 1. There are a lot of villages in CA > 2. Settlements in AU are more thinly spread. > 3. 200 might be too high. The problem being it is a lot of work to get > population numbers for places too small to register on the UCL. > > > _______________________________________________ > Talk-au mailing list > Talk-au@openstreetmap.org > https://lists.openstreetmap.org/listinfo/talk-au _______________________________________________ Talk-au mailing list Talk-au@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-au
