What are the benefits of multiple updates in isam? about lio-sam

[hunkyu]

@narutojxl isam update can speed up convergence many times, I feel that in your case, more times isam update is okay

[TixiaoShan]

@narutojxl @hunkyu
The update time is really a personal preference for me. 5 times will help the isam converge faster but may cause a performance problem.

[narutojxl]

Hi @hunkyu, do you figure out the reason?
5 times update in my computer Intel® Core™ i7-8700 CPU @ 3.20GHz × 12, will lead to the trajectory choppy like this picture. There is a little large delay, although only one update, but the trajectory is not choppy and smoother compared to 5 times update. I test with rosbag play casual_walk.bag -r 1

[narutojxl]

Thank you @hunkyu.

[narutojxl]

• The large delay phenomenon is because default rviz config show /lio_sam/mapping/cloud_registered and /lio_sam/mapping/map_local, do not show this two topic.
• map frame and odom frame is the same frame, in code we can comment tfMap2Odom.sendTransform(tf::StampedTransform(map_to_odom, thisImu.header.stamp, "map", "odom")); in imuHandler() of imuPreintegration.cpp, and then in rviz, we set the odom is the Global fixed frame.
• About the oscillation in above picture. I found it only occurs in the xy plane. I try to comment the repetitive isam->update() from line 579 to line 582, and from line 1265 to line 1269, floowing author saied above. The oscillation is moderate, but still exist. Do you know the reason @TixiaoShan and @hunkyu ? Thanks a lot!