Executing slam and navigation: topics functionality

The displays determined by the configuration file rviz_conf.vcg and their descriptions are the following:

1. Floor scan (laser scan): Shows data from a laser scan, with different options for rendering modes, accumulation, etc. sensor_msgs/LaserScan

2. Grid (Grid): Displays a 2D or 3D grid along a plane

3. Obstacles (Grid cells): Displays the obstacles that the navigation stack sees in its costmap. For the robot to avoid collision, the robot footprint should never intersect with a cell that contains an obstacle. nav_msgs/GridCells

4. Inflated obstacles (Grid Cells): Displays obstacles in the navigation stack's costmap inflated by the inscribed radius of the robot. For the robot to avoid collision, the center point of the robot should never overlap with a cell that contains an inflated obstacle. nav_msgs/GridCells

5. Map (Map): Displays a map on the ground plane. nav_msgs/OccupancyGrid

6. Global Plan (Path): Displays the portion of the global plan that the local planner is currently pursuing. nav_msgs/Path

7. Local Plan (Path): Displays the trajectory associated with the velocity commands currently being commanded to the base by the local planner.

8. Current goal (Pose): Displays the goal pose that the navigation stack is attempting to achieve. geometry_msgs/PoseStamped

9. Localisation (Pose Array): Draws a "cloud" of arrows, one for each pose in a pose array. geometry_msgs/PoseArray

10. Robot Footprint (Polygon): Displays the footprint of the robot. geometry_msgs/Polygon

If we open rxgraph we can see that most of the above displays are topics published by the move_base_node and they are subscribing to the rviz node.

If we sk rosnode to display information about the move_base_node it can tell us more clearly which topics it published and to which of them it is subscribing as well as the messages over which they communicate:

Node [/move_base_node]

Publications:
* /move_base_node/local_costmap/obstacles [nav_msgs/GridCells]
* /move_base_node/NavfnROS/NavfnROS_costmap/obstacles [nav_msgs/GridCells]
* /move_base_node/current_goal [geometry_msgs/PoseStamped]
* /move_base_node/global_costmap/unknown_space [nav_msgs/GridCells]
* /move_base_node/local_costmap/inflated_obstacles [nav_msgs/GridCells]
* /move_base_node/NavfnROS/NavfnROS_costmap/robot_footprint [geometry_msgs/PolygonStamped]
* /move_base_node/TrajectoryPlannerROS/global_plan [nav_msgs/Path]
* /move_base_node/local_costmap/voxel_grid [costmap_2d/VoxelGrid]
* /move_base/result [move_base_msgs/MoveBaseActionResult]
* /move_base_node/global_costmap/inflated_obstacles [nav_msgs/GridCells]
* /move_base_node/TrajectoryPlannerROS/local_plan [nav_msgs/Path]
* /move_base/status [actionlib_msgs/GoalStatusArray]
* /cmd_vel [geometry_msgs/Twist]
* /move_base_node/global_costmap/obstacles [nav_msgs/GridCells]
* /rosout [roslib/Log]
* /move_base/goal [move_base_msgs/MoveBaseActionGoal]
* /move_base_node/NavfnROS/plan [nav_msgs/Path]
* /move_base_node/local_costmap/unknown_space [nav_msgs/GridCells]
* /move_base_node/NavfnROS/NavfnROS_costmap/inflated_obstacles [nav_msgs/GridCells]
* /move_base_node/local_costmap/robot_footprint [geometry_msgs/PolygonStamped]
* /move_base/feedback [move_base_msgs/MoveBaseActionFeedback]
* /move_base_node/global_costmap/robot_footprint [geometry_msgs/PolygonStamped]
* /move_base_node/NavfnROS/NavfnROS_costmap/unknown_space [nav_msgs/GridCells]

Subscriptions:
* /time [unknown type]
* /move_base_simple/goal [geometry_msgs/PoseStamped]
* /move_base/goal [move_base_msgs/MoveBaseActionGoal]
* /base_scan [sensor_msgs/LaserScan]
* /map [nav_msgs/OccupancyGrid]
* /tf [tf/tfMessage]
* /clock [roslib/Clock]
* /odom [nav_msgs/Odometry]
* /move_base/cancel [unknown type]
* /reset_time [unknown type]
* /tf_message [unknown type]


This can be done for everyone of the nodes that is running.