PP3

PP3.3 Time sync using 2 velodyne laserscanners using ntp server by GPS receiver

Usage

1. roscore

2. for 64E: rosrun nodelet nodelet standalone velodyne_pointcloud/CloudNodelet _calibration:=/home/jie/catkin_ws/src/velodyne/velodyne_pointcloud/params/64e_utexas.yaml for VLP16: rosrun nodelet nodelet standalone velodyne_pointcloud/CloudNodelet _calibration:=/home/jie/catkin_ws/src/velodyne/velodyne_pointcloud/params/VLP16db.yaml

3. rosrun sync_velodyne_pcl sync_velodyne_pcl_node

4. rosbag play

5. rviz use frame velodyne

hints

for pcap 1. make sure Note 1 is done. rosrun velodyne_driver velodyne_node _model:=VLP16 _pcap:=/home/jie/23012019-14.pcap

#Note: Changed the line 290 of input.cc of velodyne_driver to get the real timestamp from pcap

•        pkt->stamp = ros::Time::now();
  

•        pkt->stamp = ros::Time(header->ts.tv_sec, header->ts.tv_usec * 1000);
  

Changed line 17-18 of pointcloudXYZIR.cc to add the info of azimuth, which used for correction of points

• point.azimuth = azimuth;
  

• point.distance = distance;
  

Changed line 32-34 of point_types.h to add definition of azimuth, distance, and timestamp

• uint16_t azimuth; ///< 0-35999>, divide by 100 to get degrees
• float distance;
• time_t timestamp; ///< timestamp> used for syncronization

Magic Notes

It's not necessary to define a new message type, just add some new attributes to the pcl::point class then it will be directly forwarded, with no need to change the message size