To use real camera to detect aruco, it's necessary to install some packages first. - sudo apt install ros-kinetic-usb_cam - sudo apt install ros-kinetic-camera-calibration - sudo apt install ros-kinetic-aruco-detect - sudo apt install ros-kinetic-fiducials - sudo apt install ros-kinetic-fiducial-msgs And, this code is for starting 2 detect node with 1 camera, because we want to use 2 different aruco setup.