Include(Menus/MapBuildingStack) RosdocHeader(gmapping) TableOfContents(3)
Package Summary
The gmapping package provides laser-based SLAM (Simultaneous Localization and Mapping). Using slam_gmapping, you can create a 2-D occupancy grid map (like a building floorplan) from laser and pose data collected by a mobile robot.
This is mostly a third party package; the underlying GMapping library is [http://openslam.org/gmapping.html external documented]. Look there for details on many of the parameters listed below.
To use gmapping, you need a mobile robot that provides odometry data and is equipped with a horizontally-mounted, fixed, laser range-finder. gmapping will attempt to transform each incoming scan into the odometry frame; make sure that all necessary transforms are available. Normally there are two transforms involved:
base_link -> odom : provided by the odometry system (e.g., the driver for the mobile base)
base_link -> base_laser : a fixed value, broadcast periodically by mechanism_control, or a tf/transform_sender
Example
To make a map from a robot with a laser publishing scans on the base_scan topic:
rosrun gmapping slam_gmapping scan:=base_scan
ROS API
Subscribed topics
scan (sensor_msgs/LaserScan) : Laser scans to create the map from
Advertised services
dynamic_map (nav_msgs/GetMap) : Call this service to get the map data
Parameters used
- ~inverted_laser (default: false) : Is the laser right side up (scans are ordered CCW), or upside down (scans are ordered CW)?
- ~throttle_scans (default: 1) : Process 1 out of every this many scans (set it to a higher number to skip more scans)
- ~base_frame (default: "base_link") : The frame attached to the mobile base.
- ~map_frame (default: "map") : The frame attached to the map.
- ~odom_frame (default: "odom") : The frame attached to the odometry system.
- ~map_update_interval_ (default: 5.0) : How long (in seconds) between updates to the map. Lowering this number updates the occupancy grid more often, at the expense of greater computational load.
- ~maxUrange (default: 80.0) : The maximum usable range of the laser. A beam is cropped to this value.
- ~sigma (default: 0.05) : The sigma used by the greedy endpoint matching
- ~kernelSize (default: 1) : The kernel in which to look for a correspondence
- ~lstep (default: 0.05) : The optimization step in translation
- ~astep (default: 0.05) : The optimization step in rotation
- ~iterations (default: 5) : The number of iterations of the scanmatcher
- ~lsigma (default: 0.075) : The sigma of a beam used for likelihood computation
- ~ogain (default: 3.0) : Obstacle gain (?)
- ~lskip (default: 0) : Number of beams to skip in each scan.
- ~srr (default: 0.1) : Odometry error in translation as a function of translation (rho/rho)
- ~srt (default: 0.2) : Odometry error in translation as a function of rotation (rho/theta)
- ~str (default: 0.1) : Odometry error in rotation as a function of translation (theta/rho)
- ~stt (default: 0.2) : Odometry error in rotation as a function of rotation (theta/theta)
- ~linearUpdate (default: 1.0) : Process a scan each time the robot translates this far
- ~angularUpdate (default: 0.5) : Process a scan each time the robot rotates this far
- ~resampleThreshold (default: 0.5) : The neff based resampling threshold (?)
- ~particles (default: 30) : Number of particles in the filter
- ~xmin (default: -100.0) : Initial map size
- ~ymin (default: -100.0) : Initial map size
- ~xmax (default: 100.0) : Initial map size
- ~ymax (default: 100.0) : Initial map size
- ~delta (default: 0.05) : Processing parameters (resolution of the map)
- ~llsamplerange (default: 0.01) : Translational sampling range for the likelihood
- ~llsamplestep (default: 0.01) : Translational sampling range for the likelihood
- ~lasamplerange (default: 0.005) : Angular sampling range for the likelihood
- ~lasamplestep (default: 0.005) : Angular sampling step for the likelihood
tf API
Required transforms
(the frame attached to incoming scans) -> base_link
base_link -> odom
Provided transforms
map - > odom
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