// 局部的子目标 (transformed plan最后一个元素)
tf::Stamped<tf::Pose> goal_point;
tf::poseStampedMsgToTF(transformed_plan.back(), goal_point);
robot_goal_.x() = goal_point.getOrigin().getX();
robot_goal_.y() = goal_point.getOrigin().getY();

if (cfg_.trajectory.global_plan_overwrite_orientation)
{
    robot_goal_.theta() = estimateLocalGoalOrientation(global_plan_, goal_point, 
       goal_idx,  tf_plan_to_global);
  // overwrite/update goal orientation of the transformed plan with the actual goal
   // (enable using the plan as initialization)
  transformed_plan.back().pose.orientation = tf::createQuaternionMsgFromYaw(robot_goal_.theta());
}
else
    robot_goal_.theta() = tf::getYaw(goal_point.getRotation());

// plan only contains the goal, 一般在导航的最后出现size是1的情况
// 用实际的机器人位姿更新 transformed plan 的起点(allows using the plan as initial trajectory)
if (transformed_plan.size()==1) 
{    // 插入起点，但不初始化
  transformed_plan.insert(transformed_plan.begin(), geometry_msgs::PoseStamped() );
}
tf::poseTFToMsg(robot_pose, transformed_plan.front().pose); // 把起点更新为 机器人当前位姿

参数global_plan_overwrite_orientation为True时，执行estimateLocalGoalOrientation()， 将未来一段的规划的姿态角的平均值返回为估计的局部目标姿态

transformed_plan.back()就是所谓的 local goal ，但是遇到需要终点转弯时，local goal的朝向不是最终的goal的朝向，仍然是规划的