Given the lat/long coordinates, how can we find out the city/country?

geolocation geocoding geospatial geo
ming yeow picture ming yeow · May 28, 2011 · Viewed 209k times · Source

For example if we have these set of coordinates

"latitude": 48.858844300000001,
"longitude": 2.2943506,

How can we find out the city/country?

Answer

Michael Borgwardt picture Michael Borgwardt · Jun 15, 2011

Another option:

  • Download the cities database from http://download.geonames.org/export/dump/
  • Add each city as a lat/long -> City mapping to a spatial index such as an R-Tree (some DBs also have the functionality)
  • Use nearest-neighbour search to find the closest city for any given point

Advantages:

  • Does not depend on an external server to be available
  • Very fast (easily does thousands of lookups per second)

Disadvantages:

  • Not automatically up to date
  • Requires extra code if you want to distinguish the case where the nearest city is dozens of miles away
  • May give weird results near the poles and the international date line (though there aren't any cities in those places anyway

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