Geohashing

geo.js

var lat, lon;

if ('geolocation' in navigator) {
  navigator.geolocation.getCurrentPosition(function(position) {
    lat = position.coords.latitude;
    lon = position.coords.longitude;

    console.log('lat: ' + lat); 
    console.log('lon: ' + lon);
    console.log('geohash: ' + geohash(lat, 0) + '' + geohash(lon, 0));
  });
}

function geohash(coord, resolution) {
  var rez = Math.pow(10, resolution || 0);
  return Math.floor(coord * rez) / rez;
}

geo.md

An example of how you can define geohash grids for users' locations

At resolution 0, each grid size is approx 111km x 111km (circumference of the earth 40,075km/360deg). Resolution 1 gives 11km x 11km grids.

The example below is for SoMa district in San Francisco at lat: 37.7834462, lon: -122.39952480000001 (Geohash grid is 37-123).