a googlemaps v2 encoded polyline to a list of coordinates (for use with the backward v3)

polyline decode

// Decode an encoded polyline into a list of lat/lng tuples.
function decodeLine (encoded) {
  var len = encoded.length;
  var index = 0;
  var array = [];
  var lat = 0;
  var lng = 0;

  while (index < len) {
    var b;
    var shift = 0;
    var result = 0;
    do {
      b = encoded.charCodeAt(index++) - 63;
      result |= (b & 0x1f) << shift;
      shift += 5;
    } while (b >= 0x20);
    var dlat = ((result & 1) ? ~(result >> 1) : (result >> 1));
    lat += dlat;

    shift = 0;
    result = 0;
    do {
      b = encoded.charCodeAt(index++) - 63;
      result |= (b & 0x1f) << shift;
      shift += 5;
    } while (b >= 0x20);
    var dlng = ((result & 1) ? ~(result >> 1) : (result >> 1));
    lng += dlng;

    array.push([lat * 1e-5, lng * 1e-5]);
  }

  return array;
}