ROS Programming: Building Powerful Robots

Understanding how the laser sends data in ROS

To check whether the node is sending data, use rostopic, as shown here:

    $ rostopic list
  

You will see the following topics as the output:

    /diagnostics
    /hokuyo_node/parameter_descriptions
    /hokuyo_node/parameter_updates
    /rosout
    /rosout_agg
    /scan
  

The /scan topic is the topic where the node is publishing. The type of data used by the node is shown here:

    $ rostopic type /scan
  

You will then see the message type used to send information about the laser:

    sensor_msgs/LaserScan
  

You can see the structure of the message using the following command:

    $ rosmsg show sensor_msgs/LaserScan
  

To learn a little bit more about how the laser works and what data it is sending, we are going to use the rostopic ...