hector_slam

The map_to_image_node converts occupancy grid maps (nav_msgs/OccupancyGrid) into images (sensor_msgs/Image) using image_transport. This allows for transmitting map data with significantly lower bandwidth by leveraging image compression plugins.

It provides two types of image outputs:

1. Full Map: A single image representing the entire occupancy grid.
2. Tile Map: A localized image centered around the robot's current position, useful for low-bandwidth remote monitoring.

Required Inputs:

• map (topic): Subscribes to nav_msgs/OccupancyGrid.
• pose (topic): Subscribes to geometry_msgs/PoseStamped (required for the tile-based map).

Outputs:

• map_image/full (topic): The full map as a MONO8 encoded image.
• map_image/tile (topic): A localized tile around the robot as a MONO8 encoded image.

The geotiff_node supports a plugin system via pluginlib. You can implement the hector_geotiff::MapWriterPluginInterface to draw custom information (like robot trajectories, object models, or other sensor data) onto the generated GeoTIFF map.

To use a plugin, include its name in the plugins parameter of the geotiff_node as a space-separated string.

The hector_mapping node is the primary entrypoint for the Hector SLAM mapping system. It initializes the hector_slam ROS node and instantiates the HectorMappingRos class, which manages the mapping lifecycle and ROS communication. To use this node, you typically run it via a ROS launch file or the command line, ensuring that the necessary sensor data (like laser scans) and odometry (if used) are being published on the expected topics.

# Example of running the node via rosrun (assuming the package is built and sourced)
rosrun hector_mapping hector_mapping_node

The hector_trajectory_server node can be configured using the following private ROS parameters to define coordinate frames and update frequencies:

The TrajectoryMapWriter plugin for hector_geotiff allows you to draw the robot's trajectory onto a GeoTIFF map. It retrieves trajectory data via a ROS service. You can configure the service name used to fetch the trajectory and the RGB color of the drawn path using ROS parameters under the plugin's private namespace.

Note: The plugin expects a service of type hector_nav_msgs/GetRobotTrajectory to be available.

<!-- Example ROS parameter configuration -->
<param name="trajectory_plugin" type="hector_geotiff_plugins/TrajectoryMapWriter">
  <param name="service_name" value="trajectory" />
  <param name="path_color_r" value="120" />
  <param name="path_color_g" value="0" />
  <param name="path_color_b" value="240" />
</param>

The trajectory_recovery_info service is used to find a path segment that leads out of a specific radius from a given pose. This is useful for recovery behaviors when a robot is stuck.

Service Type: hector_nav_msgs/GetRecoveryInfo

Request Fields:

• request_time: The timestamp of the robot pose to evaluate.
• request_radius: The radius within which the recovery path must exit.

Response Fields:

• req_pose: The pose at the requested time.
• radius_entry_pose: The pose where the trajectory first exited the requested radius.
• trajectory_radius_entry_pose_to_req_pose: A nav_msgs/Path containing the poses from the radius entry point to the requested pose.

The HectorMappingRos interface provides several ROS services to control the mapping lifecycle, including resetting the map, restarting the SLAM process, and pausing/resuming scan processing.

Available Services

The trajectory service allows clients to retrieve the full recorded trajectory stored by the server.

Service Type: hector_nav_msgs/GetRobotTrajectory