Functionality of the topics used in do-slam-navigation.launch

1) Run do-slam-navigation.launch

roslaunch launch/do-slam-navigation.launch

2) In a new terminal run rxgraph.

The nodes involved when launching do-slam-navigation.launch are the following:

/amcl
/Gmapping
/move_base_node
/Stage_Sim
/Teleop_Base
/TF_Broadcaster
/rosout

We can see how nodes communicate each other by messages through topics with the following diagram (rxgraph):



3) We can see using rxgraph to wich topic each node sobscribes or publishes. Fow example if we click on the node /Stage_Sim we get this info:

Node [/Stage_Sim]
Publications:
* /base_scan [sensor_msgs/LaserScan]
* /rosout [roslib/Log]
* /tf [tf/tfMessage]
* /clock [roslib/Clock]
* /odom [nav_msgs/Odometry]
* /base_pose_ground_truth [nav_msgs/Odometry]

Subscriptions:
* /clock [roslib/Clock]
* /cmd_vel [geometry_msgs/Twist]

Services:
* /Stage_Sim/set_logger_level
* /Stage_Sim/get_loggers
Pid: 14092
Connections:
* topic: /rosout
* to: /rosout
* direction: outbound
* transport: TCPROS
* topic: /tf
* to: /Gmapping
* direction: outbound
* transport: TCPROS
* topic: /tf
* to: /move_base_node
* direction: outbound
* transport: TCPROS
* topic: /tf
* to: /amcl
* direction: outbound
* transport: TCPROS
* topic: /base_scan
* to: /move_base_node
* direction: outbound
* transport: TCPROS
* topic: /clock
* to: /Stage_Sim
* direction: outbound
* transport: INTRAPROCESS
* topic: /clock
* to: /Gmapping
* direction: outbound
* transport: TCPROS
* topic: /clock
* to: /TF_Broadcaster
* direction: outbound
* transport: TCPROS
* topic: /clock
* to: /move_base_node
* direction: outbound
* transport: TCPROS
* topic: /clock
* to: /amcl
* direction: outbound
* transport: TCPROS
* topic: /clock
* to: /Teleop_Base
* direction: outbound
* transport: TCPROS
* topic: /clock
* to: http://oscar-laptop:56712/
* direction: inbound
* transport: INTRAPROCESS
* topic: /cmd_vel
* to: http://oscar-laptop:45548/
* direction: inbound
* transport: TCPROS
* topic: /cmd_vel
* to: http://oscar-laptop:58957/
* direction: inbound
* transport: TCPROS

Then we can see that it publishes in these topics:

* /base_scan [sensor_msgs/LaserScan]
* /rosout [roslib/Log]
* /tf [tf/tfMessage]
* /clock [roslib/Clock]
* /odom [nav_msgs/Odometry]
* /base_pose_ground_truth [nav_msgs/Odometry]

And subscribes to these other topics:
* /clock [roslib/Clock]
* /cmd_vel [geometry_msgs/Twist]

-----

As seen on the rxgraph the topics involved are:

/clock "It is used to published simulated time within a runtime system."
/tf "Current transform tree. This is the normal /tf topic."
/map "Get the map data from this topic, which is latched, and updated periodically."
/cmd_vel "velocity commands to differentially drive the position of the robot."
/rosout "Standard ROS topic for publishing logging messages."
/base_scan