Fix outdated build instructions (closes cartographer-project#1531). (c…

…artographer-project#1537)

Signed-off-by: Michael Grupp <[email protected]>

docs/source/compilation.rst

@@ -42,14 +42,14 @@ On Ubuntu Focal with ROS Noetic use these commands to install the above tools:
 .. code-block:: bash
 
     sudo apt-get update
-    sudo apt-get install -y python3-wstool python3-rosdep ninja-build
+    sudo apt-get install -y python3-wstool python3-rosdep ninja-build stow
 
 On older distributions:
 
 .. code-block:: bash
 
     sudo apt-get update
-    sudo apt-get install -y python-wstool python-rosdep ninja-build
+    sudo apt-get install -y python-wstool python-rosdep ninja-build stow
 
 After the tools are installed, create a new cartographer_ros workspace in 'catkin_ws'.
 
@@ -61,20 +61,25 @@ After the tools are installed, create a new cartographer_ros workspace in 'catki
     wstool merge -t src https://raw.githubusercontent.com/cartographer-project/cartographer_ros/master/cartographer_ros.rosinstall
     wstool update -t src
 
-Install cartographer_ros' dependencies (proto3 and deb packages).
+Now you need to install cartographer_ros' dependencies.
+First, we use ``rosdep`` to install the required packages.
 The command 'sudo rosdep init' will print an error if you have already executed it since installing ROS. This error can be ignored.
 
 .. code-block:: bash
 
-    src/cartographer/scripts/install_proto3.sh 
     sudo rosdep init
     rosdep update
     rosdep install --from-paths src --ignore-src --rosdistro=${ROS_DISTRO} -y
 
-This builds Cartographer from the latest HEAD of the master branch.
-If you want a specific version, you need to change the version in the cartographer_ros.rosinstall.
+    # Only on Ubuntu 16 / ROS Kinetic: src/cartographer/scripts/install_proto3.sh 
+
+Cartographer uses the `abseil-cpp`_ library that needs to be manually installed using this script:
+
+.. code-block:: bash
 
-Additionally, uninstall the ros abseil-cpp using
+    src/cartographer/scripts/install_abseil.sh 
+
+Due to conflicting versions you might need to uninstall the ROS abseil-cpp using
 
 .. code-block:: bash
 
@@ -85,3 +90,8 @@ Build and install.
 .. code-block:: bash
 
     catkin_make_isolated --install --use-ninja
+
+This builds Cartographer from the latest HEAD of the master branch.
+If you want a specific version, you need to change the version in the cartographer_ros.rosinstall.
+
+.. _abseil-cpp: https://abseil.io/