README.md

Reverse Country Code

A reverse geocoder that converts latitude and longitude coordinates to country information such as names, ISO codes and locales.

Usage

ReverseGeocoder geocoder = new ReverseGeocoder();
geocoder.getCountry(51.507222, -0.1275).ifPresent(country -> {
    System.out.println(country.iso());        // GB
    System.out.println(country.iso3());       // GBR
    System.out.println(country.isoNumeric()); // 826
    System.out.println(country.name());       // United Kingdom
    System.out.println(country.area());       // 244820.0
    System.out.println(country.population()); // 62348447
    System.out.println(country.continent());  // EU
    List<Locale> locales = country.locales();
    System.out.println(locales.get(0));       // en_GB
    System.out.println(locales.get(1));       // cy_GB
    System.out.println(locales.get(2));       // gd
});

Dataset

Country information and boundary data comes from GeoNames.

Accuracy

97.92% when ran against the GeoNames data set for cities with a population > 15000.

Performance

~3 μs average to look up city from the GeoNames data set on a 13" MacBook Pro (i5-5257U) using a single thread. The retained heap size for ReverseGeocoder is ~7.5 MB.

Algorithms

Country bounding boxes are loaded into R-Trees using the Sort-Tile-Recursive algorithm. Determining if a point lies within a polygon is performed using the PNPOLY algorithm.

Gradle tasks

Build jar:

./gradlew assemble

Download new Geonames data:

./gradlew updateCountryInfo updateShapes

Run benchmarks:

./gradlew jmh

Generate new baseline test data:

./gradlew generateBaseline