Encodes / decodes a latlng object to 10 characters with 6 decimal (< 0.5 meter) precision

latLngCoder.js

/**
 * Encode/decode latlng
 */
var latLngCoder = (function(map) { 
    map = map ? map : "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-"; 
    var self = {}; 
    var encodenum = function(num, len) { 
        enc = []; 
        while (num > 0) { 
            enc.unshift(map[num % map.length]); 
            num = Math.floor(num / map.length); 
        }
        while (len && enc.length < len--) enc.unshift("0");
        return enc.join("");
    }
    var decodenum = function(code) {
        dec = 0;
        for (var k = 0; k < code.length; ++k) {
            dec *= map.length;
            dec += map.indexOf(code[k]);
        }
        return dec;
    }; 

    /**
     * Encode a latlng object
     * @param c {lat:123.456789,lng:123.456789}
     * @return  "1234512345"
     */
    self.encode = function(c) {
        return encodenum(Math.round(c.lat * 1000000), 5) + encodenum(Math.round(c.lng * 1000000), 5);
    };
    
    /**
     * Same as encode, only reversed
     * @param c encode string
     * @return object with lat and lng
     */
    self.decode = function(c) {
        console.log(decodenum(c.substr(0,5)));
        return {lat: decodenum(c.substr(0,5)) / 1000000, lng: decodenum(c.substr(5)) / 1000000};
    };
    return self;

}());