docs: refer to the localization tutorial

docs/source/localization.rst

@@ -53,4 +53,41 @@ Write me!
 
 3. Localization with particle filtering
 ----------------------------------------
-Write me!
+To localize with a particle filter (PF) you will need:
+
+1. A metric map (the ``.mm`` file) of the environment. Built as described in: :ref:`building-maps`.
+2. To publish that map using `mrpt_map_server <https://github.com/mrpt-ros-pkg/mrpt_navigation/tree/ros2/mrpt_map_server/>`_.
+3. Launch `mrpt_pf_localization <https://github.com/mrpt-ros-pkg/mrpt_navigation/tree/ros2/mrpt_pf_localization>`_ and configure it
+   to read from wheels odometry (if they exist), the input sensors (e.g. LiDAR), GPS (GNSS) if present. This node will subscribe to
+   the published metric map and use the sensors to publish updates on the robot pose in the `map` frame.
+
+.. note::
+
+   Do **NOT** set the raw LiDAR pointcloud as input for the PF. It is just too large and it must be subsampled first.
+   We can use `mrpt_pointcloud_pipeline <https://github.com/mrpt-ros-pkg/mrpt_navigation/tree/ros2/mrpt_pointcloud_pipeline>`_
+   for such task, as can be seen in the tutorial below.
+
+3.1. Tutorial
+================
+A complete demonstration has been put together on: https://github.com/MOLAorg/mola_warehouse_pf_tutorial
+
+.. dropdown:: Run tutorial
+  :open:
+
+    Clone the tutorial package (which already includes a prebuilt ``.mm``), make sure of having all dependencies,
+    build and run it:
+
+   .. code-block:: bash
+
+         cd ~/ros2_ws/src
+         git clone https://github.com/MOLAorg/mola_warehouse_pf_tutorial.git
+
+         cd ~/ros2_ws
+         rosdep install --from-paths src --ignore-src -r -y
+
+         colcon build --symlink-install --cmake-args -DCMAKE_BUILD_TYPE=RelWithDebInfo
+
+         ros2 launch mola_warehouse_pf_tutorial tutorial_launch.py
+
+
+