Offline reverse geocoding on iOS

Question

There are lots of existing questions relating to this issue, but I have looked at as many of them as I could find and did not get an answer.

I'm trying to perform an offline reverse geocoding lookup on iOS based on a latitude and longitude. I'd like to be able to provide a latitude and longitude, and be provided with the country in which that point lies. I can do this with Geonames (such as: http://api.geonames.org/countryCode?lat=45.03&lng=8.2&username=demo), but I need a similar ability offline, without Internet functionality on the device.

CLLocation does not provide offline services that work reliably enough for what I'm doing, it relies on caches made while you were previously online, etc. Messy.

I've tried this: https://github.com/drodriguez/reversegeocoding but haven't had any luck, it requires some slightly complex / confusing Terminal installations using something called Thor which I've never heard of, and was throwing up a variety of errors, so I bailed on it.

I've found a few downloadable maps, but these seem to be even more complicated, and worryingly, hundreds of megabytes or even gigabytes in size – much beyond the scope of an iOS app. I only need countries, nothing smaller than that (cities, streets, locations, etc.) so I think I should be able to get a much smaller file.

So my key question is: is there some pre-existing database or tool, preferably with iOS support, that I can feed a latitude/longitude, and get a country? And, if not, what steps should I take to get such functionality working on my own?

Thanks in advance.

Answer 1

ReverseGeocodeCountry is a simple lightweight offline country reverse geocoder for iOS, it has a static JSON file with country polygon data that is used to reverse geocode any lat/lng:

https://github.com/krisrak/ios-offline-reverse-geocode-country

Answer 2

The "Countries of the World" is a .csv text file with countries, coordinates, localised country names, capitals and other information. It seems to be free to use. You just have to import it into an SQLite database.

Edit Just noticed you want reverse geocoding. The database would only be good for forward geocoding.

You can download shapefiles for all countries at http://www.gadm.org/download. If you download a .kmz, you can unpack it to a list of coordinates for the borders. You could probably take every 5th or 10th coordinate to get smaller size (with less accuracy).

Answer 3

Just in case I can suggest another good written offline geocoding library. https://github.com/Alterplay/APOfflineReverseGeocoding