Sorry about the duplicate "many"; that was a result of sloppy editing.
-------Original Email------- Subject :Re: [OSM-talk] Most complete cities and administrativedivisionsdatabase From :mailto:j...@jfeldredge.com Date :Wed Jan 26 12:37:14 America/Chicago 2011 In the USA (and possibly elsewhere, as well), time zone boundaries tend to be far from straight, due to politicians feeling that it would be beneficial to place A to be in time zone B, rather than time zone C. So, a time zone table would need to have many information on many locations, not just "time zone X starts at latitude Z". -------Original Email------- Subject :Re: [OSM-talk] Most complete cities and administrative divisionsdatabase From :mailto:sko...@free.fr Date :Wed Jan 26 12:22:07 America/Chicago 2011 On 11-01-26 12:13 PM, M∡rtin Koppenhoefer wrote: > 2011/1/26 Sami Dalouche<sko...@free.fr>: > > he geonames project (http://www.geonames.org/) provides over 7 million > POI, and 2 million of them are cities. > > > 2 million can IMHO only refer to all settlements, not just to cities. > There is around 7 billion people living on earth, ~ half of them in > cities. If you divide 3,5 billion people by 2 million, you get an > average of 1750 people per city. Not quite much ;-) (or they have lots > of multiple entries). Yes, actually I was using the word 'city' where I should have been using 'place' or 'settlement'. The 2 million count includes all populated places in Geonames. (and includes junk such as junctions that are tagged as populated places). >> So, more specifically, here are my questions : >> 1/ how many cities are present in OSM ? > > this is easy to answer: > http://taginfo.openstreetmap.de/keys/place#values > 492 155 village > 397 919 hamlet > 57 083 town > 44 450 suburb > 18 942 city > Wao, great tool ! So, I guess that ~1 million populated places makes OSM complete-enough for locating most important populated places. BTW, most places in geonames also have an associated timezone. Is there any freely available database of timezones with the latitudes/longitudes bounds ? This could serve as a replacement for geonames' timezone field. >> 2/ how many of these cities are also associated to polygons that delimit >> them ? > > are you asking about the city or about it's administrative boundary? > http://taginfo.openstreetmap.de/keys/boundary#values I was asking about its administrative boundary. So, after reading http://wiki.openstreetmap.org/wiki/Key:place, what I understand is that : - Cities are marked as nodes - Sometimes, there are additional ways (boundary=administrative) to delimit the administrative boundary - As a bonus, there can be relations that link the city node to its boundary. Am I right ? So now, let's go with other administrative divisions : Now, let's say I want to add an entry for Orange County. How should I do it ? Should it just appear as a boundary=administrative, or should there be some kind of node node and a relation ? > >> 3/ Are countries and administrative divisions also explicited in OSM ? (e.g. >> USA, California, Orange county, ..) > > you can do this with relations > > >> 4/ Are there polygons for these administrative divisions and countries ? > > you can get them from the relations (if the relations are there and > are clean). Have a look at type=boundary and type=multipolygon > > Cheers, > Martin Thanks for your help ! Sami Dalouche _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk -- John F. Eldredge -- j...@jfeldredge.com "Reserve your right to think, for even to think wrongly is better than not to think at all." -- Hypatia of Alexandria _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk -- John F. Eldredge -- j...@jfeldredge.com "Reserve your right to think, for even to think wrongly is better than not to think at all." -- Hypatia of Alexandria _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
