Point time calculation

[vovo-4K]

There is the t field in the Point structure:

struct EIGEN_ALIGN16 Point {
    PCL_ADD_POINT4D;
    float intensity;
    uint32_t t;
    uint16_t reflectivity;
    uint16_t ring;
    uint16_t ambient;
    uint32_t range;
    EIGEN_MAKE_ALIGNED_OPERATOR_NEW
};

https://github.com/ouster-lidar/ouster-ros/blob/19071eb14e0c8fecf0d94d1b2399aea5f44d549c/ouster-ros/include/ouster_ros/os_point.h#L23C16-L23C16

How can I calculate absolute point time using message header time and the t field?

[Samahu]

Simple, take the value of header.stamp from the published sensor_msgs::msg::PointCloud2 message and add it to the value of t field from ouster_ros::Point.

[vovo-4K]

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?

[Samahu]

ouster_ros::Point::t is represented in nanoseconds.

[liuXinGangChina]

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

[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

[liuXinGangChina]

thanks got it !