Thank you for your reply! The header.stamp is composed of two parts: an integer representing seconds and an unsigned integer representing nanoseconds. What is the ouster_ros::Point::t field dimension? Does it contain nanoseconds offset since header.stamp?

nice answer,
by the way , do you mean the sbsolute time stamp of a point = lidar.header.stamp.sec + lidar.header.stamp.nsec x 10^6 + t x 10^6
@Samahu

I think the correct formula would be: pt_absolute_ts_ns = lidar.header.stamp.sec * 10^9 + lidar.header.stamp.nsec + pt.t then you can convert that amount back to seconds if you choose to

thanks got it !