laser scan topic

Question

i install ros indigo desktop full and Turtlebot2 Ubuntu Package . when i do $rostopic list i cant find /laser/scan topic . there's something like additional installation or other name of laser scan topic ?

listed topics :

/camera/depth/camera_info
/camera/depth/image_raw
/camera/depth/points
/camera/parameter_descriptions
/camera/parameter_updates
/camera/rgb/camera_info
/camera/rgb/image_raw
/camera/rgb/image_raw/compressed
/camera/rgb/image_raw/compressed/parameter_descriptions
/camera/rgb/image_raw/compressed/parameter_updates
/camera/rgb/image_raw/compressedDepth
/camera/rgb/image_raw/compressedDepth/parameter_descriptions
/camera/rgb/image_raw/compressedDepth/parameter_updates
/camera/rgb/image_raw/theora
/camera/rgb/image_raw/theora/parameter_descriptions
/camera/rgb/image_raw/theora/parameter_updates
/clock
/cmd_vel_mux/active
/cmd_vel_mux/input/navi
/cmd_vel_mux/input/safety_controller
/cmd_vel_mux/input/switch
/cmd_vel_mux/input/teleop
/cmd_vel_mux/parameter_descriptions
/cmd_vel_mux/parameter_updates
/depthimage_to_laserscan/parameter_descriptions
/depthimage_to_laserscan/parameter_updates
/gazebo/link_states
/gazebo/model_states
/gazebo/parameter_descriptions
/gazebo/parameter_updates
/gazebo/set_link_state
/gazebo/set_model_state
/joint_states
/laserscan_nodelet_manager/bond
/mobile_base/commands/motor_power
/mobile_base/commands/reset_odometry
/mobile_base/commands/velocity
/mobile_base/events/bumper
/mobile_base/events/cliff
/mobile_base/sensors/bumper_pointcloud
/mobile_base/sensors/core
/mobile_base/sensors/imu_data
/mobile_base_nodelet_manager/bond
/odom
/rosout
/rosout_agg
/scan
/tf
/tf_static

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Originally posted by EGYRos on ROS Answers with karma: 1 on 2018-03-17

Post score: 0

Answer 1

Hello EGYRos,

although I am not familiar with the Turtlebot2 Ubuntu Package (maybe you are referring to the turtlebot ROS package?) and cannot find the package named turtlebot2 I would like to point out that there is a /scan topic on your list. Try:

rostopic info /scan

I am guessing you will find that messages being passed in this topic are of type sensor_msgs/LaserScan. If you look at the depthimage_to_laserscan package you will find that it publishes laser scan on topic /scan.
If you would like your laser scan to be published on another topic, you can remap it:

rosrun depthimage_to_laserscan depthimage_to_laserscan scan:=laser/scan

However, that would be a quick fix. I am guessing that /laser prefix is here because of the laser namespace and maybe it would be better practice to include is as a namespace tag in your launch file. An example of setting namespace in launch file can be found here.

Furthermore, I can see you are using RGBD camera and depthimage_to_laserscan package to obtain laser scan like measurements.
Just a heads up, depthimage_to_laserscan is a lazy subscriber meaning it won't subscribe to a camera image topic and camera info topic unless there are no subscribers to /scan topic. The easiest way to ensure that there is a subscriber is to simply visualize it in rviz.

If you have any further question, feel free to ask it.

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Originally posted by dljubic with karma: 516 on 2018-03-17

This answer was ACCEPTED on the original site

Post score: 0

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Original comments

Comment by EGYRos on 2018-03-18:
Hello dljubic

Ya i get it , thanks a lot it is very useful.

Comment by dljubic on 2018-03-19:
No problem, I am glad to help! :)
Please mark the answer as correct if it solved your problem.