code: static double computeAngleBetween(IGeoPoint from, IGeoPoint to) {
          return distanceRadians(toRadians(from.getLatitude()), toRadians(from.getLongitude()),
              toRadians(to.getLatitude()), toRadians(to.getLongitude()));
      }
docs: Returns the angle between two IGeoPoints, in radians. This is the same as the distance
  on the unit sphere.