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Comment by Pxtl | Hacker News Reader

Since I obviously have some OSM developers in the room, can somebody point me to the right place to query against OSM mapping data? That is, if I want to get all one-way streets and stop-lights within my area, how do I do that? I've tried the various tools that send you a subset of the map (they don't seem to work) and the "download the whole OSM map and play with the XML" seems like a good way to choke on the data... Anybody got pointers?

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A query like "one-way streets and stop-lights within my area" is perfect for the Overpass API: http://wiki.openstreetmap.org/wiki/Overpass_API

The best UI for Overpass is http://overpass-turbo.eu/

Overpass is great: All hospitals in Western Cape of South Africa: http://overpass-turbo.eu/s/on

Else there are more manageable regional extracts of OpenStreetMap XML: http://download.geofabrik.de/

If you're wanting to query the data importing into PostGIS is a fairly straightforward way to do it. And you don't have to download the whole planet in one go.

+1 to this. Metro Extracts: http://metro.teczno.com/ along with osm2pgsql: http://wiki.openstreetmap.org/wiki/Osm2pgsql is the way to go.

Be aware that those extracts are squares around the cities - they're not exact city border outlines. This means that you can't just use the data without concern for whether the things you're gathering are actually within the city or not.

I haven't found a very simple way to get everything within exact city borders, yet. This is the process I've been going with so far: https://github.com/JamesChevalier/cities#cities

That is a very useful resource; thank you.

Some cities make shapefiles available for urban growth boundaries and city limits. It's worth enquiring. But be aware that some cities city limits are not simple polygons; depending on local ordinances you can see islands, internal voids and peninsulas attached with zero width stems.

True! Like Houston, TX ... which looks a little like the flying spaghetti monster ... http://nominatim.openstreetmap.org/details.php?place_id=3675...

The poly files that you get from the process outlined in the readme file will include islands/voids. It's pretty cool.

Well remember OSM is an international project, so trying to find one definition of "city" and "border of a city" is hard. Some places (like USA) seem to use "city" as a hard solid thing, other places (eg UK / ireland) don't.

Yeah - OSM goes a long way in categorizing different levels of "area in which people live" based on population density. http://wiki.openstreetmap.org/wiki/Key:place

Except that the place tag isn't always based on population size. In some places, (e.g. UK), a common cultural definition of a "city" is archaic, and depends if the place has a Cathedral and/or charter from the monarch.

I give you the "city" of St. David's: http://www.openstreetmap.org/browse/node/3216768 It's in Wales, UK, and is tagged as "place=city". It's a small town of ~2,000 people. It has a charter from the monarch, and a cathedral. The "note" tag in OSM says: "the "city" is on paper, what's on the ground is a small town".

Humanity is complicated. :)

heh, true!

I've been playing with place names & http://overpass-turbo.eu/ ... I seem to be getting the best results with "city|hamlet|metropolis|town|village", although some states like Alaska & Hawaii still don't return much with this scope.

In Alaska, a lot of places are labeled as County. In Hawaii, a lot of places are labeled as Other.

UK isn't the only place with weird "cities".

Greenhorn, Oregon is designated as a city but has a 2010 census population of zero. Though now unicorporated, Tenny, Minnesota, was a city and had a peak population of 180 people in 1910 but now is down to 5 (2010 census).

A friend of mine has recently started a service for providing processed OSM data based on user's requirements for a small fee. Check it out - http://opencagedata.com/

I've been speaking to them a bit about city-specific data, and they've been incredibly helpful & knowledgable.

Why am I not surprised that you're interested in seeing data on one-way streets in your area? :)

I've been meaning to dig more deeply into OSM for a while now, and this may be the kick I need to do it.

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