Latency troubleshooting with rtabmap-ros

Posted by Alan on
URL: http://official-rtab-map-forum.206.s1.nabble.com/Latency-troubleshooting-with-rtabmap-ros-tp6939.html

Hi,

I am mapping with an L515 lidar on rtabmap-ros and I am encountering some mapping latency that I can't really explain. Odometry is done with ICP via libpointmatcher and I am getting consistently ~0.03s update frequency

[ INFO] [1600664613.655947447]: Odom: ratio=0.046694, std dev=0.015367m|0.015367rad, update time=0.033356s

For some reason however the map will be delayed up to several seconds, even though it looks like the RTABMap node is running at 3 hz, faster than my 2 hz detection rate:

[ INFO] [1600664613.892001514]: rtabmap (140): Rate=0.50s, Limit=0.100s, RTAB-Map=0.3242s, Maps update=0.0025s pub=0.0000s (local map=72, WM=72)

As you can see I have set the TimeThr to 100 ms to try and force the mapping node closer to real time, but this doesn't appear to have an effect.
The rest of my settings are essentially as described in the launch file in this github comment:
https://github.com/introlab/rtabmap/issues/574#issuecomment-689149729
I have also set General/decimation0 to 20 to try and speed things up.

Running on ROS melodic with a Ryzen 9 4900HS CPU. I was previously able to map with the L515 on this computer using ICP and F2M without any lag until the map got too large, but I didn't back up my old .launch file. Now I have significant latency from the beginning, though I am not sure what has changed. Do you have any suggestions for tracking down the bottleneck?
Thanks!