Mapping with SLAM Toolbox and EasyNav

This HowTo explains how to create a 2D occupancy map using SLAM Toolbox and store it for later use with the Simple Stack in EasyNavigation (EasyNav).

Warning

The Simple stack is a minimal example, with very basic algorithms. For real use, map with the Costmap stack instead (Mapping with the Costmap Stack): the steps are the same.

Overview 

This tutorial uses the Kobuki PlayGround and the Simple Stack, which relies on binary occupancy grids (0 for free, 1 for occupied).

The workflow consists of:

Running the simulator.
Starting SLAM Toolbox to build the map.
Using EasyNav to receive and save the map through the Simple Maps Manager.
Using the saved map for navigation.

Setup 

Build EasyNav and the Kobuki PlayGround as described in Getting Started.

SLAM Toolbox can be installed via apt:

sudo apt install ros-${ROS_DISTRO}-slam-toolbox

or built from source: https://github.com/SteveMacenski/slam_toolbox

Step-by-Step Instructions 

Launch the simulator (with or without GUI)

ros2 launch easynav_playground_kobuki_worlds gazebo_sim.launch.yaml gui:=false

Launch SLAM Toolbox

SLAM Toolbox reads the laser on /scan, but the Kobuki publishes it on /scan_raw. Copy its default parameter file and set scan_topic: /scan_raw in it:

cp /opt/ros/${ROS_DISTRO}/share/slam_toolbox/config/mapper_params_online_async.yaml ~/slam_kobuki.yaml
# edit ~/slam_kobuki.yaml: scan_topic: /scan_raw

Then launch it:

ros2 launch slam_toolbox online_async_launch.py \
  use_sim_time:=true slam_params_file:=$HOME/slam_kobuki.yaml

SLAM Toolbox publishes the map (nav_msgs/msg/OccupancyGrid) on /map.

Start EasyNav in mapping mode

In mapping mode only the Maps Manager does something; the rest of the nodes use dummy plugins. The Kobuki PlayGround ships this configuration as params/simple.mapping.params.yaml. The Simple Maps Manager receives external maps on /maps_manager_node/simple/incoming_map, so remap SLAM Toolbox’s /map to it:

ros2 run easynav_system system_main --ros-args \
  --params-file $(ros2 pkg prefix easynav_playground_kobuki)/share/easynav_playground_kobuki/params/simple.mapping.params.yaml \
  -r /maps_manager_node/simple/incoming_map:=/map

The relevant part of the configuration is the maps manager, with no map file:

maps_manager_node:
  ros__parameters:
    use_sim_time: true
    map_types: [simple]
    simple:
      freq: 10.0
      plugin: easynav_simple_maps_manager/SimpleMapsManager

Open RViz2

ros2 run rviz2 rviz2 \
  -d $(ros2 pkg prefix easynav_playground_kobuki)/share/easynav_playground_kobuki/rviz/easynav_simple.rviz \
  --ros-args -p use_sim_time:=true

Teleoperate the robot to build the map
```
ros2 run teleop_twist_keyboard teleop_twist_keyboard
```
As you move the robot, SLAM Toolbox publishes the growing map on /map, and the Simple Maps Manager republishes it as its own map.

Saving and Reusing the Map 

Save the generated map
```
ros2 service call /maps_manager_node/simple/savemap std_srvs/srv/Trigger
```
With no map configured (package and map_path_file), the map is stored in /tmp/default.map.
Move the map into a package of your workspace, for example my_maps_pkg, in a directory that the package installs (e.g. maps/):
```
mv /tmp/default.map ~/easynav_ws/src/my_maps_pkg/maps/house.map
```

Update your navigation parameters to load it. The map is located with package (a ROS 2 package, searched in its share directory) and map_path_file (the path inside it); both are needed:

maps_manager_node:
  ros__parameters:
    use_sim_time: true
    map_types: [simple]
    simple:
      freq: 10.0
      plugin: easynav_simple_maps_manager/SimpleMapsManager
      package: my_maps_pkg
      map_path_file: maps/house.map

You can now use this map with the Simple Stack (see Navigating with SimpleStack and EasyNav).

Notes 

The Simple Maps Manager saves and loads maps using its own lightweight text format (a single .map file: width, height, resolution and origin on the first line, followed by the binary occupancy data). It is not the YAML + PGM format used by Nav2. If you need a Nav2-compatible YAML + PGM map, use the Costmap Stack instead (Mapping with the Costmap Stack).
You can visualize both SLAM and EasyNav map topics in RViz2 to confirm synchronization.

Mapping with SLAM Toolbox and EasyNav

Overview

Setup

Step-by-Step Instructions

Saving and Reusing the Map

Notes