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Overview

An example video can be seen here:

Further video examples are available in this playlist: http://www.youtube.com/playlist?list=PL0E462904E5D35E29

Details can also be found in this paper:

@INPROCEEDINGS{KohlbrecherMeyerStrykKlingaufFlexibleSlamSystem2011,
  author = {S. Kohlbrecher and J. Meyer and O. von Stryk and U. Klingauf},
  title = {A Flexible and Scalable SLAM System with Full 3D Motion Estimation},
  year = {2011},
  month = {November},
  booktitle = {Proc. IEEE International Symposium on Safety, Security and Rescue Robotics (SSRR)},
  organization = {IEEE},
}

available here .

Hardware Requirements

To use hector_mapping, you need a source of sensor_msgs/LaserScan data (for example a Hokuyo UTM-30LX LIDAR or bagfiles). The node uses tf for transformation of scan data, so the LIDAR does not have to be fixed related to the specified base frame. Odometry data is not needed.

ROS API

hector_mapping

hector_mapping is a node for LIDAR based SLAM with no odometry and low computational resources. For simplicity, the ROS API detailed below provides information about the commonly used options from a user perspective, but not all options that are available for debugging purposes.

Subscribed Topics

scan (sensor_msgs/LaserScan)

• The laser scan used by the SLAM system.

syscommand (std_msgs/String)

• System command. If the string equals "reset" the map and robot pose are reset to their inital state.

Published Topics

map_metadata (nav_msgs/MapMetaData)

• Get the map data from this topic, which is latched, and updated periodically.

map (nav_msgs/OccupancyGrid)

• Get the map data from this topic, which is latched, and updated periodically

slam_out_pose (geometry_msgs/PoseStamped)

• The estimated robot pose without covariance

poseupdate (geometry_msgs/PoseWithCovarianceStamped)

• The estimated robot pose with an gaussian estimate of uncertainty

Services

dynamic_map (nav_msgs/GetMap)

• Call this service to get the map data.

reset_map (std_srvs/Trigger)

• Call this service to reset the map, and hector will start a whole new map from scratch. Notice that this doesn't restart the robot's pose, and it will restart from the last recorded pose.

pause_mapping (std_srvs/SetBool)

• Call this service to stop/start processing laser scans.

restart_mapping_with_new_pose (hector_mapping/ResetMapping)

• Call this service to reset the map, the robot's pose, and resume mapping (if paused)

Parameters

~base_frame (string, default: base_link)

• The name of the base frame of the robot. This is the frame used for localization and for transformation of laser scan data.

~map_frame (string, default: map_link)

• The name of the map frame.

~odom_frame (string, default: odom)

• The name of the odom frame.

~map_resolution (double, default: 0.025)

• The map resolution [m]. This is the length of a grid cell edge.

~map_size (int, default: 1024)

• The size [number of cells per axis] of the map. The map is square and has (map_size * map_size) grid cells.

~map_start_x (double, default: 0.5)

• Location of the origin [0.0, 1.0] of the /map frame on the x axis relative to the grid map. 0.5 is in the middle.

~map_start_y (double, default: 0.5)

• Location of the origin [0.0, 1.0] of the /map frame on the y axis relative to the grid map. 0.5 is in the middle.

~map_update_distance_thresh (double, default: 0.4)

• Threshold for performing map updates [m]. The platform has to travel this far in meters or experience an angular change as described by the map_update_angle_thresh parameter since the last update before a map update happens.

~map_update_angle_thresh (double, default: 0.9)

• Threshold for performing map updates [rad]. The platform has to experience an angular change as described by this parameter of travel as far as specified by the map_update_distance_thresh parameter since the last update before a map update happens.

~map_pub_period (double, default: 2.0)

• The map publish period [s].

~map_multi_res_levels (int, default: 3)

• The number of map multi-resolution grid levels.

~update_factor_free (double, default: 0.4)

• The map update modifier for updates of free cells in the range [0.0, 1.0]. A value of 0.5 means no change.

~update_factor_occupied (double, default: 0.9)

• The map update modifier for updates of occupied cells in the range [0.0, 1.0]. A value of 0.5 means no change.

~laser_min_dist (double, default: 0.4)

• The minimum distance [m] for laser scan endpoints to be used by the system. Scan endpoints closer than this value are ignored.

~laser_max_dist (double, default: 30.0)

• The maximum distance [m] for laser scan endpoints to be used by the system. Scan endpoints farther away than this value are ignored.

~laser_z_min_value (double, default: -1.0)

• The minimum height [m] relative to the laser scanner frame for laser scan endpoints to be used by the system. Scan endpoints lower than this value are ignored.

~laser_z_max_value (double, default: 1.0)

• The maximum height [m] relative to the laser scanner frame for laser scan endpoints to be used by the system. Scan endpoints higher than this value are ignored.

~pub_map_odom_transform (bool, default: true)

• Determine if the map->odom transform should be published by the system.

~output_timing (bool, default: false)

• Output timing information for processing of every laser scan via ROS_INFO.

~scan_subscriber_queue_size (int, default: 5)

• The queue size of the scan subscriber. This should be set to high values (for example 50) if logfiles are played back to hector_mapping at faster than realtime speeds.

~pub_map_scanmatch_transform (bool, default: true)

• Determines if the scanmatcher to map transform should be published to tf. The frame name is determined by the 'tf_map_scanmatch_transform_frame_name' parameter.

~tf_map_scanmatch_transform_frame_name (string, default: scanmatcher_frame)

• The frame name when publishing the scanmatcher to map transform as described in the preceding parameter.

Required tf Transforms

<the frame attached to incoming scans> → base_frame

• usually a fixed value, broadcast periodically by a robot_state_publisher, or a tf static_transform_publisher.

Provided tf Transforms

map → odom

• the current estimate of the robot's pose within the map frame (only provided if parameter "pub_map_odom_transform" is true).