Display PointCloud Rviz

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Check that you have a proper header: it should have time stamp, so the ROS thinks the data is fresh. Make sure you do something like this msg.header.stamp = ros::Time::now();

You gave to your point cloud frame_id "my_cloud". The thing is that ROS should now how to transform from the world coordinates to your local coordinate system. So you should cast the transformation. The easiest way to do so is to use console command which will broadcast transformation to ROS

static_transform_publisher x y z yaw pitch roll frame_id child_frame_id period_in_ms

In your case that would be

static_transform_publisher 0 0 0 0 0 0 base_link my_cloud 1

Hope this will help.