Geohash

Native Swift geohash package supporting binary and character encoding

I also have a Rust version

Geohashes are represented internally as 64 bit integers. A hash can be constructed either using character precision (up to 12 characters) or binary precision (up to 32 bits per angle).

GeohashBits(location: Location(longitude: -0.1, latitude: 51.5), characterPrecision: 12).hash()
=> "gcpuvxr1jzf"
GeohashBits(location: Location(longitude: -0.1, latitude: 51.5), bitPrecision: 26).hash()
=> "gcpuvxr1jz" 

Note that the last value is truncated at 10 characters (50 bits) even though the "full" representation is 52 bits total. Since the character encoding is Base32, we require 5 bits for each.

The Geohash boundaries and centroids are correctly handled when the character representation provides a different number of bits for latitude and longitude (e.g. geohash 7 which has 18 bits of longitude and 17 bits of latitude).

GeohashBits(hash: "u10hfr2").boundingBox().center()
=> (longitude: 0.0995635986328125, latitude: 51.5004730224609)

This is the same answer you will get from PostGIS

select ST_AsText(ST_PointFromGeoHash('u10hfr2'));
st_astext                  
--------------------------------------------
POINT(0.0995635986328125 51.5004730224609)

The library also supports computing neighbors

GeohashBits(hash: "u10hfr2c4pv").neighbor(.north).hash()
=> "u10hfr2c60j"

Acknowledgements

Based on the Redis implementation,

• Copyright (c) 2013-2014, yinqiwen [email protected]
• Copyright (c) 2014, Matt Stancliff [email protected]
• Copyright (c) 2015-2016, Salvatore Sanfilippo [email protected]