Reading sensor_msgs/PointCloud2 data and visualizing the points

Dear all,

I am connecting Matlab ros with Classical ROS. In command I run the roscore and copy same URL in

> rosinit('http://IMAG-MARVIN:11311/')

Now I can list all the topics by

> rostopic('list')

that gives the output

/clock                
/img_node/nearir_image
/img_node/range_image 
/img_node/reflec_image
/img_node/signal_image
/os_cloud_node/imu    
/os_cloud_node/points 
/os_node/imu_packets  
/os_node/lidar_packets
/rosout               
/rosout_agg           
/tf_static    

Now I want to visualize /os_cloud_node/points which are of type

  /img_node/nearir_image         229       sensor_msgs/Image          'std_msgs/Header Header↵  uint32 Seq↵  Time Stamp↵  char FrameId↵uint32 Height↵uint32 Width↵char Encoding↵uint8 IsBigendian↵uint32 Step↵uint8[] Data↵'                                                                                                                                                                                                                                                         
    /img_node/range_image          229       sensor_msgs/Image          'std_msgs/Header Header↵  uint32 Seq↵  Time Stamp↵  char FrameId↵uint32 Height↵uint32 Width↵char Encoding↵uint8 IsBigendian↵uint32 Step↵uint8[] Data↵'                                                                                                                                                                                                                                                         
    /img_node/reflec_image         229       sensor_msgs/Image          'std_msgs/Header Header↵  uint32 Seq↵  Time Stamp↵  char FrameId↵uint32 Height↵uint32 Width↵char Encoding↵uint8 IsBigendian↵uint32 Step↵uint8[] Data↵'                                                                                                                                                                                                                                                         
    /img_node/signal_image         229       sensor_msgs/Image          'std_msgs/Header Header↵  uint32 Seq↵  Time Stamp↵  char FrameId↵uint32 Height↵uint32 Width↵char Encoding↵uint8 IsBigendian↵uint32 Step↵uint8[] Data↵'                                                                                                                                                                                                                                                         
    /os_cloud_node/imu            2288       sensor_msgs/Imu            'std_msgs/Header Header↵  uint32 Seq↵  Time Stamp↵  char FrameId↵geometry_msgs/Quaternion Orientation↵  double X↵  double Y↵  double Z↵  double W↵double[9] OrientationCovariance↵geometry_msgs/Vector3 AngularVelocity↵  double X↵  double Y↵  double Z↵double[9] AngularVelocityCovariance↵geometry_msgs/Vector3 LinearAcceleration↵  double X↵  double Y↵  double Z↵double[9] LinearAccelerationCovariance↵'
    /os_cloud_node/points          229       sensor_msgs/PointCloud2    'std_msgs/Header Header↵  uint32 Seq↵  Time Stamp↵  char FrameId↵uint32 Height↵uint32 Width↵sensor_msgs/PointField[] Fields↵  uint8 INT8↵  uint8 UINT8↵  uint8 INT16↵  uint8 UINT16↵  uint8 INT32↵  uint8 UINT32↵  uint8 FLOAT32↵  uint8 FLOAT64↵  char Name↵  uint32 Offset↵  uint8 Datatype↵  uint32 Count↵logical IsBigendian↵uint32 PointStep↵uint32 RowStep↵uint8[] Data↵logical IsDense↵'                
    /os_node/imu_packets          2289       ouster_ros/PacketMsg       'uint8[] Buf↵'                                                                                                                                                                                                                                                                                                                                                                                                 
    /os_node/lidar_packets       18310       ouster_ros/PacketMsg       'uint8[] Buf↵'                                                                                                                                                                                                                                                                                                                                                                                                 
    /rosout                         12       rosgraph_msgs/Log          'int8 DEBUG↵int8 INFO↵int8 WARN↵int8 ERROR↵int8 FATAL↵std_msgs/Header Header↵  uint32 Seq↵  Time Stamp↵  char FrameId↵int8 Level↵char Name↵char Msg↵char File↵char Function↵uint32 Line↵char[] Topics↵'                                                                                                                                                                                                        
    /tf_static                       1       tf2_msgs/TFMessage         'geometry_msgs/TransformStamped[] Transforms↵  std_msgs/Header Header↵    uint32 Seq↵    Time Stamp↵    char FrameId↵  char ChildFrameId↵  geometry_msgs/Transform Transform↵    geometry_msgs/Vector3 Translation↵      double X↵      double Y↵      double Z↵    geometry_msgs/Quaternion Rotation↵      double X↵      double Y↵      double Z↵      double W↵'                                            

I can't figure it out. Please Help

Answer 1

[Cam Salzberger]

Hello Junaid,

If you create a subscriber for the topic of interest, you can get the messages on that topic either in the subscriber's callback (NewMessageFcn) that you supply, or by checking the LatestMessage property of the subscriber. Then you can use rosPlot on the message to display them. See this example for a walkthrough on the specialized message handling.

-Cam