ruby on rails - Calculate to and fro track distance in leaflet -

i using leaflet-rails gem (0.7.4) , need calculate track distance in case path , fro. in our application, upload gpx file , display points using leaflet. calculate track distance first , last point in case of , fro path track distance comes out zero. here points array of coordinates (latitude , longitude).

def deg2rad deg   return deg * math::pi / 180; end  def fetch_track_distance  distance = 0  start_point = self.points.first  end_point = self.points.last   if start_point.present? && end_point.present?   dlat = self.deg2rad(end_point.latitude - start_point.latitude)   dlon = self.deg2rad(end_point.longitude - start_point.longitude)    r = math::sin(dlat/2) *     math::sin(dlat/2) +     math::cos(self.deg2rad(start_point.latitude)) *     math::cos(self.deg2rad(end_point.latitude)) *     math::sin(dlon/2) *     math::sin(dlon/2);   c = 2 * math::atan2(math.sqrt(r), math::sqrt(1-r));   mdist = radian * c;   distance = (mdist/1000) if mdist.present?  end   return distance.round(3) end   

thanks in advance.