Thank you @imdsafi09 for your report! 👍🏻
I have a few points of concern to mention.

• Your rqt_graph includes /predict_with_cloud_node, which is implemented in the melodic-devel branch. Given that your operating environment is Noetic, you should be using the noetic-devel branch. It's probable that melodic-devel might work well in a Noetic environment, but switching to the correct branch is advisable...
• Please confirm if data is flowing correctly by echoing the /yolo_result, /detection_cloud and /detection_marker.
• Make sure the callback function in tracker_with_cloud_node is called as expected. Logging in the following way should make this clear:

  void TrackerWithCloudNode::syncCallback(const sensor_msgs::CameraInfo::ConstPtr& camera_info_msg,
                                          const sensor_msgs::PointCloud2ConstPtr& cloud_msg,
                                          const ultralytics_ros::YoloResultConstPtr& yolo_result_msg)
  {
    ROS_INFO("HELLO!!");
    ros::Time current_call_time = ros::Time::now();
    ...
  }

  If the timestamp of /yolo_result published by the tracker_node is significantly different from /kitti/camera_color_left/camera_info or /kitti/velo/pointcloud, this may prevent syncCallback() from being called. Consider increasing the queue size to see if this improves the situation:

  camera_info_sub_.subscribe(nh_, camera_info_topic_, 10);
  lidar_sub_.subscribe(nh_, lidar_topic_, 10);
  yolo_result_sub_.subscribe(nh_, yolo_result_topic_, 10);
  sync_ = boost::make_shared<message_filters::Synchronizer<ApproximateSyncPolicy>>(1);

Best regards,

Hello @Alpaca-zip
Thank you for your feedback. I shifted from Nvidia Agx_orin (ROS-Noetic) to my PC, where I am using ROS-Melodic. After changing the queue size as followed, it is now working properly.

camera_info_sub_.subscribe(nh_, camera_info_topic_, 1);
lidar_sub_.subscribe(nh_, lidar_topic_, 1);
yolo_result_sub_.subscribe(nh_, yolo_result_topic_, 1);
sync_ = boost::make_shared<message_filters::Synchronizer>(100);

However, when I am doing the same changes in noetic branch I am facing the error showing in the screenshot. Could you please let me know what could be the possible solution.

I have two additional questions.

1. The 3D bounding boxes appear to have a fixed orientation regardless of the 2D bounding box shape. Is there a solution to have a 3D bounding box oreintation similar to the 2D one? Is it possible to solve this issue by using "Oriented Bounding Boxes Object Detection [https://docs.ultralytics.com/tasks/obb/]?
2. I have an Ouster lidar (Os-128), which provides signal images (mono-16). I am able to subscribe to the lidar signal images for yolov8 and publish 2D bounding boxes. However, lidar is not a standard camera, and thus the camera info topic is missing. Therefore, I want to determine what could be a possible solution to this problem.

Best regards,