    // Location
    // --------
    MM.Location = function(lat, lon) {
        this.lat = parseFloat(lat);
        this.lon = parseFloat(lon);
    };

    MM.Location.prototype = {
        lat: 0,
        lon: 0,
        toString: function() {
            return "(" + this.lat.toFixed(3) + ", " + this.lon.toFixed(3) + ")";
        }
    };

    // returns approximate distance between start and end locations
    //
    // default unit is meters
    //
    // you can specify different units by optionally providing the
    // earth's radius in the units you desire
    //
    // Default is 6,378,000 metres, suggested values are:
    //
    // * 3963.1 statute miles
    // * 3443.9 nautical miles
    // * 6378 km
    //
    // see [Formula and code for calculating distance based on two lat/lon locations](http://jan.ucc.nau.edu/~cvm/latlon_formula.html)
    MM.Location.distance = function(l1, l2, r) {
        if (!r) {
            // default to meters
            r = 6378000;
        }
        var deg2rad = Math.PI / 180.0,
            a1 = l1.lat * deg2rad,
            b1 = l1.lon * deg2rad,
            a2 = l2.lat * deg2rad,
            b2 = l2.lon * deg2rad,
            c = Math.cos(a1) * Math.cos(b1) * Math.cos(a2) * Math.cos(b2),
            d = Math.cos(a1) * Math.sin(b1) * Math.cos(a2) * Math.sin(b2),
            e = Math.sin(a1) * Math.sin(a2);
        return Math.acos(c + d + e) * r;
    };

    // Interpolates along a great circle, f between 0 and 1
    //
    // * FIXME: could be heavily optimized (lots of trig calls to cache)
    // * FIXME: could be inmproved for calculating a full path
    MM.Location.interpolate = function(l1, l2, f) {
        if (l1.lat === l2.lat && l1.lon === l2.lon) {
            return new MM.Location(l1.lat, l1.lon);
        }
        var deg2rad = Math.PI / 180.0,
            lat1 = l1.lat * deg2rad,
            lon1 = l1.lon * deg2rad,
            lat2 = l2.lat * deg2rad,
            lon2 = l2.lon * deg2rad;

        var d = 2 * Math.asin(
            Math.sqrt(
              Math.pow(Math.sin((lat1 - lat2) / 2), 2) +
              Math.cos(lat1) * Math.cos(lat2) *
              Math.pow(Math.sin((lon1 - lon2) / 2), 2)));
        var bearing = Math.atan2(
            Math.sin(lon1 - lon2) *
            Math.cos(lat2),
            Math.cos(lat1) *
            Math.sin(lat2) -
            Math.sin(lat1) *
            Math.cos(lat2) *
            Math.cos(lon1 - lon2)
        )  / -(Math.PI / 180);

        bearing = bearing < 0 ? 360 + bearing : bearing;

        var A = Math.sin((1-f)*d)/Math.sin(d);
        var B = Math.sin(f*d)/Math.sin(d);
        var x = A * Math.cos(lat1) * Math.cos(lon1) +
          B * Math.cos(lat2) * Math.cos(lon2);
        var y = A * Math.cos(lat1) * Math.sin(lon1) +
          B * Math.cos(lat2) * Math.sin(lon2);
        var z = A * Math.sin(lat1) + B * Math.sin(lat2);

        var latN = Math.atan2(z, Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2)));
        var lonN = Math.atan2(y,x);

        return new MM.Location(latN / deg2rad, lonN / deg2rad);
    };
