public NavigationOdometry()
 {
     header         = new StandardHeader();
     child_frame_id = "";
     pose           = new GeometryPoseWithCovariance();
     twist          = new GeometryTwistWithCovariance();
 }
 public GeometryPoseWithCovarianceStamped()
 {
     header = new StandardHeader();
     pose   = new GeometryPoseWithCovariance();
 }