From OpenStreetMap Wiki
Jump to navigation Jump to search

When should one tag a city as a town?

I have updated the lead to clarify the difference between cities as defined by official designation and the use of the city tag in OSM. In particular to highlight when it is appropriate to tag a settlement as town in OSM even though it is official designated at a city. Lets talk about it if we need to work on this more. PeterIto (talk) 11:13, 14 February 2013 (UTC)

This lack of understanding is becoming a serious problem. I find numerous regions (edited by many different people) where tiny populated places of a few hundred people are being upgraded to place=city, "because that place is a city". iD says in its pop-up help,
  • city: The largest urban settlement or settlements within the territory.
  • town: An important urban centre, between a village and a city in size.
  • village: A settlement with between 1,000 and 10,000 inhabitants.
  • hamlet: A settlement with less than 100-200 inhabitants.
  • locality: A named place that has no population.
This is all fine and good -- if you know to look for those tags, and if you understand that these tags are used to rank importance of a place based on population and distance from other populated places of importance. A new iD user who looks at a populated place and thinks 'But that's a city', and types in city may very well tag it that way.
The problem is that OSM's place tag names often overlap with the formal administrative titles of populated places, and it's a confusion I can't see going away.
If we really want to end this kind of confusion, it would help a lot if we simply used one tag, like this:
  • place=settlement (Used regardless of the size or title of a human settlement.)
  • name=Howard (Obvious. Used the same as it is today.)
  • layer=0 (Optional. Used exactly how layer is today with other data sets. One number higher than the other means that settlement is 'rendered on top' when a render conflict exists. Assumed zero by default.)
  • population=9999 (When layer numbers match, population can be used to determine importance.)
  • admin_level=0 (Used how it's used today. Doesn't determine render importance, but is used by nominatim for administrative boundary relation purposes.)
  • admin_title=town/village/city etc., an optional User Defined field. A default title is assumed when an admin_level exists, and this field does not. (Not used to determine render importance at all, but could be used to supplement the name of a place, like 'Village of Howard' or 'City of Appleton', or 'Acadia Parish' in Louisiana where counties don't exist at all.) These can be used by a map renderer, or by Nominatim to title a given administrative area with any name desired. Deprecates place=county/state/etc.)
I'm just tossing this idea out there as 'an idea', and I grant that a change this sweeping would be a stretch to see approved. That said, unless something like the above, or edit locks are implemented to prevent this kind of place tag upgrading, I imagine it happening for the indefinite future. Skybunny (talk) 22:32, 9 June 2014 (UTC)
I generated a formal proposal for the classification criteria here: Proposed_features/Populated_settlements_classification --Iagocasabiell (talk) 01:56, 7 September 2019 (UTC)

"Charter cities"

I have a problem with the 2018-added (fairly recently) comment by Dcapillae regarding "charter cities" in the United States: huh? First of all, some states in the USA have these, some don't (California, where he gives the example of Alameda, does). Second, this is a legal definition that classifies governance and has little to do with population or whether another city (larger or smaller) is proximate to the charter city. Third, the suggestion that we do this smacks mightily of "tagging for the renderer." Let's tag cities according to their existing definitions, guided by their population and let renderers deal with it. I propose we remove Dcapillae's suggestion. After all, OSM is about the data, not the rendering. Stevea (talk) 19:34, 22 April 2019 (UTC)
I agree with that. Although maybe not tagging for the rendering, but tagging for the "gazetteer search results." Generally, the criteria for when to use a tag shouldn't be based on it's geographical proximity to something else. Population is way more scientific and probably makes better sense to the average person. --Adamant1 (talk) 09:12, 25 April 2019 (UTC)

Population tag values of place=city nodes

I've downloaded all the place=city nodes in the database, and all the place=town and place=village in a number of countries for comparison. See Talk:Tag:place=town for details about towns and Talk:Tag:place=village for villages. I didn't download ways or relations, since most of those are duplicated by nodes (and only 14% of place=town are also mapped as an area).

It turns out that the previous suggestion on the wiki that villages have 1000 to 10k population wasn't based on the data: the median (average) village size is 500 to 1000 in most countries, and the 90% or 95% range is about 100 to 10,000k (though many villages do not have a population tag, which makes this analysis limited). Towns mostly range in population from 1k to 100k, and the median in each country ranges from as low as 3k in Canada and 4k in Greece, to as high as 30k in Japan and 50k in South Africa (I believe many smaller towns lack a population tag in South Africa, but many of the towns in Japan have a tag, so it's numbers are relatively reliable).

Looking at cities, the median city population tag value globally is 134k. I suspect that many larger cities actually have a population value for the municipality rather than for the entire urban area which is referred to by that name, but this is more of a problem for cities with population >200k. There are 9812 nodes with place=city tags globally, and 6185 (63%) have a population tag. Of these, 3838 (62%) are >100k, so 38% are less than 100k, with median of 134k worldwide (again, among those tagged with population=*). 1101 (17%) are less than 50k, 295 (5%) are less than 20k, and 194 are less than 10k (3%). Only 7 place=city have population recorded as less than 1000k.

I would suggest adding some of these statistics to the page. I believe it would be useful to add a summary something like this:

"The minimum population of a place tagged as a place=city varies depending on the country and for different regions within large countries. For this reason, it is helpful to add a population=* when possible. Currently 63% of place=city have a population tag. Of these, 95% of place=city have population=20000 or greater, and only 3% of population=* values are less than 10,000. However, a third (33%) of place=city have a population= value between 20,000 and 100,000.

This would help remind mappers to consider the local context and how the tag is used in their country or region rather than focusing on particular population cut-offs, but also give some information about values that are lower than average; e.g. places with <10k are rarely tagged as cities. I've also seen a number of places that "a city should have more than 100k population", and these numbers show that this opinion is not widely supported by current usage, at least in many countries. --Jeisenbe (talk) 01:11, 20 August 2019 (UTC)

I appreciate the fruits of research and analysis Jeisenbe presents here. With the exception of one minor typo I've corrected in his proposed Summary statement, I not only agree with it fully, I believe inclusion would benefit the Page. There are opinions that "city must be ≥100k," but where those prevail, the data bear that out (i.e., THERE, town and village are used for what other places often call city, a "small city," to be sure, but tagged place=city nonetheless due to more-local convention). I notice as this has evolved, Jeisenbe has omitted (I paraphrase and embellish somewhat) "Including population data (when known) can help determine whether 'edge cases' might be better tagged with the next place=* value up or down, as populations do change over time." I believe that (or something like it) is a helpful addition to the proposed Summary statement. Putting smart "hand-holds" like these into our wiki makes data better over time, strengthening our tagging with clear intent as more consistent. Stevea (talk) 01:56, 20 August 2019 (UTC)
I included the sentence "For this reason, it is helpful to add a population=* when possible" in the example text, which is meant to be similar to what you suggest above. I'm not sure if we should imply that an increase in population automatically warrants changing the classification of a settlement: if all of the nearby cities and towns have also gained (or lost) a similar percentage of their population, then it wouldn't be necessary. It's more that having the population=* tag lets database users make their own assumptions, especially about how to render or interpret 3 place=city with 1) population=30k 2) populatino=130k and 3) poplution=900k (most will treat the later specially, by displaying at earlier zoom levels, or placing search results higher on the list, etc, and some may distinguish between the first and second examples, but this depends on the database user). --Jeisenbe (talk) 02:03, 20 August 2019 (UTC)
Sound logic, well explained and so, "fair enough." What we fully agree upon is that "this depends on the database user," and we only slightly differ on offering the person entering the data good guidance. Again, I believe the Summary text is well-researched, well-written and deserves a place (heh) in the Page. "As is," or if others wish to offer additional suggestions. One clarification (usually gets added to "currently") would be a date to that context, like "as of August, 2019"). Stevea (talk) 02:08, 20 August 2019 (UTC)

I've added the new section now. --Jeisenbe (talk) 06:15, 24 August 2019 (UTC)