Hands-On ROS for Robotics Programming

Analyzing the ROS graph using rqt_graph

By issuing this command, you can visualize the current ROS graph:

T3 $ rqt_graph

It will show the following diagram:

raspicam_node is the root node of the package that interfaces with the physical Pi Camera. It publishes images in the /raspicam_node/image/compressed topic. The other node, imv_view, from the process in the T2 terminal, launches a window where you can watch the live stream (as shown in the preceding section).

Finally, inspecting the topic's raspicam_node provides the following:

T4 $ rostopic list | grep raspicam_node/raspicam_node/camera_info/raspicam_node/image/compressed/raspicam_node/parameter_descriptions ...