Techniques for offline reverse geocoding on a mobile device?

Question

I am working on a mobile mapping application (currently iOS, eventually Android) - and I am struggling with how to best support reverse geocoding from lat/long to Country/St

Answer 1

If you're looking for an approach based on a quadtree, try Yggdrasil. It generates a quadtree based on country polygon data. A Ruby example script can be found here.

Answer 2

I can suggest good written offline geocoding 3rd party library. https://github.com/Alterplay/APOfflineReverseGeocoding

Answer 3

Radven

You will need to get the Shapefiles (lat/lng outline) of all the administrative entities (US states, countries, etc). There are a lot of public domain sources for these. For example, the NOAA has shapefiles for US states and territories you can download:

http://www.nws.noaa.gov/geodata/catalog/national/html/us_state.htm

Once you got the shapefiles, you can use a shapefile reader to test if a lat/lng is within a shape. There are open source readers in C, just google. I seen stuff at sourceforge for shapefiles, but have not used these myself.

The Team at OpenGeoCode.Org