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hyye / lio-mapping

Implementation of Tightly Coupled 3D Lidar Inertial Odometry and Mapping (LIO-mapping)
https://sites.google.com/view/lio-mapping
GNU General Public License v3.0
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msg_time_delay meaning #81

Closed magehrig closed 3 years ago

magehrig commented 3 years ago

Hi @hyye

My Situation: I have PointCloud2 messages (at 10 Hz) with header timestamps that correspond to the last packet of the scan, as set as default in the velodyne ros driver launch script. Now I would like to set msg_time_delay accordingly, but its meaning is unclear to me, even after reading issue https://github.com/hyye/lio-mapping/issues/33

My questions: Could you explain the implications of setting msg_time_delay? (what happens if I set it to a value X?) And how should I set it in my case?

How far I got: You use this value here in the code to set laser_odom_time, however, the 'corrected' timestamp is not used to process the data. Why is the 'corrected' timestamp not used in further processing?

In my case, I think the former addition of msg_time_delay to the already provided header timestamp does not seem to make sense because my timestamp is according to the last packet.

Thanks for open-sourcing your code!

magehrig commented 3 years ago

I somewhat circumvent this problem by setting the timestamps of the lidar scans (before using this framework) to the middle of the scan. Then I set the msg_time_delay to 0.