need timestamp for every point in the point cloud

[hanzheteng]

Some user reached out for this feature request. I will document some solutions in this issue.

[hanzheteng]

The default point type used in Velodyne LiDAR is velodyne_pointcloud::PointXYZIR, which does not have a field called time. This information may be needed in some LiDAR-inertial odometry algorithms (e.g., Fast-LIO). One workaround is to compute a rough timestamp for each point and save them into the intensity field.

  for (size_t i = 0; i < cloud->size(); ++i) {
    cloud->points[i].intensity = float(double(i) / double(cloud->size()));
  }  // you can use static_cast if you want

Alternatively, if we want to create a new point type named PointXYZIRT that includes the time field, we can create a header file as follows and use it in the program.

#ifndef MY_PC_POINT_TYPES_H
#define MY_PC_POINT_TYPES_H

#include <pcl/point_types.h>

namespace velodyne_pointcloud
{
  struct PointXYZIRT
  {
    PCL_ADD_POINT4D;
    PCL_ADD_INTENSITY;
    float    time;
    uint16_t ring;
    EIGEN_MAKE_ALIGNED_OPERATOR_NEW
  } EIGEN_ALIGN16;

}; // namespace velodyne_pointcloud

POINT_CLOUD_REGISTER_POINT_STRUCT(velodyne_pointcloud::PointXYZIRT,
                                  (float, x, x)
                                  (float, y, y)
                                  (float, z, z)
                                  (float, intensity, intensity)
                                  (float, time, time)
                                  (uint16_t, ring, ring))
#endif // MY_PC_POINT_TYPES_H

[hanzheteng]

FYI, the documentation for velodyne LiDAR driver is here:

• https://docs.ros.org/en/electric/api/velodyne_pointcloud/html/structvelodyne__pointcloud_1_1PointXYZIR.html
• https://docs.ros.org/en/electric/api/velodyne_pointcloud/html/point__types_8h_source.html