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Twin Towns/Friendship Cities

'Morning, fellow mappers...

I am currently passing some spare time filling in a largely blank area of the map in my home vicinity and am going for maximum detail. As such I've been minded that my local town is twinned with two European cities and a namesake city in the US. It occurs that this information may be useful to hold in the OSM database so, having not found anything pre-existing in OSM Wiki that covers this, I have added an experimental tag to the place=town nodes in two towns local to me that have twin towns (called "friendship cities" in Europe):-

With single twin:

is_in=Somerset, England, UK
twin_town=Le Lion d'Angers

With multiple twins:

is_in:district=Taunton Deane
is_in=Somerset, England, UK
note=Taunton is not a city, County Town of Somerset
twin_town=Lisieux;Königslutter;Taunton, Ma

Note in the second example that the town is twinned with an identically named town/city in Massachusetts, USA. Is it them desirable to include the OSM country code with the twinned city name? For example "Lisieux(FR);Königslutter(DE);Taunton, Ma(US)". I would contend that it is necessary to include the state abbreviation for US cities as they seem to have a lot of place names repeated in different states. It could be further extended for mappers adding twin-town information to place=town/city tags to then go to the twinned towns and cities and edit their place=town tags to add their twinned towns/cities and thus create an indexable bi-directional network of twin-towns around the world.

Whilst I may be a reasonably dab hand at editing the map now I'm new to editing OSM Wiki and so have not added anything to the main page for this tag. Also, I've no idea how one goes about generating an "official" tag or key that would render on the map or who indeed is even in charge of configuring the rendering for! At the moment I'm merely seeking the views of more seasoned Wiki-ers as to viability, utility, etc. I could see third party users of the OSM database being able to set up interactive maps with hyperlinks that take you to the twinned cities or that bring up information pages on the twins when the main town is clicked for information and so on. Then again, I read an article the other day reporting that a lot of UK local authorities are cutting their twin-town links to save money so...!

It also occurs that, if there's general agreement as to the usefulness of this information, then the "twin_town" tag would need it's own page as it can apply to other place= keys as well as place=town.

--John Grubb (talk) 06:37, 11 September 2018 (UTC)

I support having such a tag, not sure what the tag name should be (sister city is more common in NA than twin town, but I have heard there are different connotations). My city has several. Also, I have not seen something like this done in other tags and maybe there is a reason for that, but why not make the reference an OSM ID number (for the municipal admin relation) instead of a name? AFAIK, the number would only change if the relation ever got deleted (and potentially remade, but not simply a reversion of the delete), so it ought be fairly stable. Arlo James Barnes (talk) 04:52, 23 September 2018 (UTC)

---Thanks for the feedback. Considering your points; OSM seems to use British English by default (colour= rather than color= for example) so twin_town would seem to be the natural tag. I would suggest it is left to wider debate by more users to settle, possibly in a vote, however - the more widely-used term would lend itself to acceptance rather than a term that might be specific to only one country (e.g. twin towns are called "friendship cities" in the rest of Europe). Not sure what an "OSM ID number" is as a reference or otherwise and presume many other mappers would be similarly hampered. What is it out, of interest? The actual twin-town name(s) seems the logical choice and also follows the "sign over the door" rule, as it is what is displayed on city limit signs.

--John Grubb (talk) 21:33, 23 September 2018 (UTC)

Average (median) population and population range for towns

I've downloaded all the towns in several countries and reviewed the population numbers. Not all towns have a population listed, but more than 75% did - though this varies by country. The analysis is just based on towns that have a population listed in OSM, which I suspect skews the numbers higher than they would be, since smaller settlements are less likely to have an official population recorded. The median (average) town size globally appears to be about 10,000. However, Canada has a median town population of about 3000 and Greece 4000, while Japan has a median of 30,000 and South Africa is 50k - and all the range in between is covered by others. There are very few towns below 1000 population, and few over 100,000 population. In most countries there are none under 2000 or over 100,000, and the majority are between 5000 and 50,000. The areas downloaded were the UK, Ireland, Portugal, Switzerland, Greece, Denmark, Finland, Ukraine, Iran, Japan, Taiwan, Indonesia, Argentina, South Africa, Canada, and several USA States (Oregon, California, Arizona, New Mexico, N and S Dakota).

I would like to use this information to update the page to say:

"the median (average) place=town population in the databse is around 10,000, but the median varies by country, from as low as 3000 to as high as 50000. Almost all place=town have a population between 2000 and 100000." --Jeisenbe (talk) 15:19, 18 August 2019 (UTC)

You should keep in mind that (a) population numbers tagged are not necessarily accurate. In many cases such numbers will be census based for the whole administrative unit and not only for the populated place in the OSM sense. And (b) the likeliness of there being a population number tagged varies with size - very small places (where the population can be directly counted or estimated by the mapper) and very large places (where population numbers are relatively well accessible from public records) are probably much more likely to have this tagged.
Given it is unlikely that there will be agreement among mappers on verifiable criteria to distinguish between town, village etc. the most important advise probably is if mappers use populated place tags on atypically large/small places to always also tag the population. --Imagico (talk) 16:48, 18 August 2019 (UTC)
This came up because another user suggested population ranges for hamlets, villages, towns and cities on Talk:Tag:place=hamlet, and also thought a new tag like "big_hamlet" was needed for places with 200 to 1000 people, since the place=village page stated (incorrectly, it appears) that a village has population 1000 to 10,000. The other user also mentioned that towns are for 10k to 100k and cities >100k - numbers that I've frequently seen elsewhere, althought they do not appear to be based on actual usage. I've responded there, and also checked the populations of cities and villages: see comments at Talk:Tag:place=village too.
In relation to this mappers should also see this discussion section: --John Grubb (talk) 23:50, 7 November 2020 (UTC)
My first thought was to updated the possible population range for villages to include 100 to 10,000 and also mention the median (usually 400 to 1000), but perhaps you are recommending we remove all mention of particular numbers, since the definition is often not based on population? Or do you think it would improve the wiki if we add mentions of the 90% ranges and median ranges for population, for place=village and place=town? Note that place=hamlet already mentions that it is usually less than 100 to 200 inhabitants. --Jeisenbe (talk) 03:47, 19 August 2019 (UTC)
I think it would definitely be good to have data on actual population of mapped populated places but that the tagged population numbers are probably on average somewhat skewed. --Imagico (talk) 09:23, 19 August 2019 (UTC)
The information for villages is less complete, so we could just add the info about the median range and 95th percentile ranges for towns, since the population numbers for towns are more often available. It's true that this information is often somewhat incorrect, but since it will be a range of 1 to 2 powers of 10, it should be ok, as long as the population numbers for towns are within one power of 10 from the correct value. And having a range for towns will also suggest something about the probable range for place=village population sizes, so it's okay if the Tag:place=village page doesn't specify a population range. --Jeisenbe (talk) 00:00, 20 August 2019 (UTC)
I've added a new section which mentions the population ranges, as well as the historical meaning of "town" as a market town for contrast. --Jeisenbe (talk) 05:51, 24 August 2019 (UTC)
I generated a formal proposal for the classification criteria here: Proposed_features/Populated_settlements_classification --Iagocasabiell (talk) 01:55, 7 September 2019 (UTC)