On 11-01-26 12:13 PM, M∡rtin Koppenhoefer wrote:
2011/1/26 Sami Dalouche<[email protected]>:
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
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