int main(int argc, char** argv)
{
	ROS_INFO("Using subscriptions demo");
	ros::init(argc, argv, "UsingSubscriptionsDemo");
	Drone d;
	d.addNavdataDemoCallback(navdata_demo_callback);
	d.addNavdataVisionDetectCallback(navdata_vd_callback);

	ros::spin(); //checks subscriptions forever

	return 0;
}