Add link to untethered operation

ros1/navigation_stack.md

@@ -1,6 +1,6 @@
 ## Navigation Stack with Actual robot
 
-stretch_navigation provides the standard ROS navigation stack as two launch files. This package utilizes gmapping, move_base, and AMCL to drive Stretch around a mapped space. Running this code will require the robot to be untethered.
+stretch_navigation provides the standard ROS navigation stack as two launch files. This package utilizes gmapping, move_base, and AMCL to drive Stretch around a mapped space. Running this code will require the robot to be [untethered](https://docs.hello-robot.com/0.2/stretch-tutorials/getting_started/untethered_operation/).
 
 
 Then run the following commands to map the space that the robot will navigate in.
@@ -68,4 +68,4 @@ roslaunch stretch_navigation mapping.launch rviz:=false teleop_type:=none
 rviz -d `rospack find stretch_navigation`/rviz/mapping.launch
 # On your machine, Terminal 2:
 roslaunch stretch_core teleop_twist.launch teleop_type:=keyboard # or use teleop_type:=joystick if you have a controller
-```
+```