Country code from a latitude longitude position (without using geocoding services)

Question

How can i get the country code from a latitude longitude position?

I know that there are many geocoding services available, but they don\'t meed my requirement becau

Answer 1

Given the number of countries (polygons) in the world, you may want to subdivide the set of country polygons to do a rough filter first (e.g., if the point is in the western and northern hemispheres, only need to check North American, Central American, and Carribean countries. That may give you a speed improvement.

Also, keep in mind that many countries consist of multiple polygons, just keep that in mind as you code.

I haven't used any of these sources for country boundary data, but checkout: http://geocommons.com/overlays/33578 and http://geospatial.edublogs.org/2010/06/29/world-country-boundary-files/

Answer 2

I assume you want the ISO 3166-1 alpha-2 country code (vs. the FIPS 10=4 which is being phased out by Dec. 2012). There are 248 countries, territories and dependencies listed by ISO. ViennaMike's approach by doing a quick filter to reduce to checking by continent sounds like a good performance approach.

You will want to use the countries shapefile to know which country the lat/lng is within (ie., check if point is within a polygon).

There are a lot of free sources (but may have commerical licensing restrictions). Here's another source from the open source project (openstreetmap)

http://downloads.cloudmade.com/

Andrew, The Team at OpenGeoCode.Org