Lab 5: Mapping and Navigation
=============================================================================


In this lab, we will use `gmapping` package for SLAM. The gmappimg algorithm
implements SLAM using a Rao- Blackwellized particle filter. It is probably the
most used SLAM algorithm in ROS. In the first part of the lab, you will use
gmapping to build your own map. In the second part, you will launch the ROS
Navigation Stack to let your robot move autonomously.

Getting Started
----------------------
Install the `navigation` ros package in your VM.

.. code-block:: bash

   sudo apt install ros-melodic-navigation

Clone the example code into your catkin workspace:

.. code-block:: bash

   cd ~/catkin_ws/src
   git clone https://github.com/cmuq-robotics/cmuq-turtlebot-remote.git


Launching the example
--------------------------------------------------

Connect to one of the robots and edit the file `connect_robot.sh` with the correct values.

Open a new terminal window and set the environment variables:

.. code-block:: bash

   source ~/connect_robot.sh


Use the tool `rostopic` to see the list of topics currently used in the network and check that you can connect to your robot.

.. code-block:: bash

   rostopic list

Launch the `teleop_key` node to move your robot:

.. code-block:: bash

   roslaunch turtlebot_teleop keyboard_teleop.launch



Part I: Using GMapping
-----------------------------------------

For the first part, use `gmapping` to build our own map. Gmapping implements a
laser-based SLAM algorithm with a particle filter. We will study SLAM in the next weeks. For now, let's
learn how to use it.

Open a new terminal window and set the environment variables:

.. code-block:: bash

   source ~/connect_robot.sh

Launch the `gmapping_demo`

.. code-block:: bash

   roslaunch gmapping_demo gmapping.launch


In a new terminal, set the environment variables and run:

.. code-block:: bash

   source ~/connect_robot.sh
   roslaunch turtlebot_rviz_launchers view_navigation.launch

You should now have an RViz window.


While moving your robot, you will observe how the map is being built.

.. image:: img/gmapping_1.png
  :width: 600
  :alt: Alternative text


When you are done, you can save the map. In a new terminal, set the environment variables and run:

.. code-block:: bash

   source ~/connect_robot.sh
   rosrun map_server map_saver -f ~/catkin_ws/src/cmuq-turtlebot-remote/turtlebot2_navigation/current_map/map

You now have a copy of the map in your catkin workspace.

Now it's time to stop gmapping and start the navigation stack.

Part II: Using the ROS navigation stack
-----------------------------------------

For the second part, you should kill all the nodes launched in the first part, including rviz.

Open a new terminal window and set the environment variables:

.. code-block:: bash

   source ~/connect_robot.sh

Launch the `navigation` stack

.. code-block:: bash

   roslaunch turtlebot2_navigation navigate.launch


In a new terminal, set the environment variables and run:

.. code-block:: bash

   source ~/connect_robot.sh
   roslaunch turtlebot_rviz_launchers view_navigation.launch

You should now have an RViz window.

Localize your robot like we did in the last lab. Then, send a goal pose and see the magic happen.