SLAM using RTABMAP

[xantho]

Hello,

I am using RTABMAP in noetic with 20.04. I get fair mapping results but I would like to improve them and work perfectly.

A few of the issues I have are:
1) it doesn't like the camera (d435i) to move at normal speed. It prefers the camera to move really slow.
    Also, even if the robot stands still I get this warning:

The time difference between rgb and depth frames is high (diff=0.033357s, rgb=1701783597.300058s, depth=1701783597.333416s). You may want to set approx_sync_max_interval lower than 0.02s to reject spurious bad synchronizations or use approx_sync=false if streams have all the exact same timestamp.

This is also the output of ntpdate -q

server 192.168.10.70, stratum 3, offset 0.861476, delay 0.03094
 5 Dec 15:42:11 ntpdate[3595]: step time server 192.168.10.70 offset 0.861476 sec

Any idea whats going on here?

After this problem I would like to start navigation.
The tutorials are pretty old and some settings are different for my case.
I followed these two websites:
http://wiki.ros.org/rtabmap_ros/Tutorials/StereoOutdoorNavigation
and I used the yaml files from this one:
https://github.com/turtlebot/turtlebot_apps/blob/indigo/turtlebot_navigation/param/costmap_common_params.yaml

for the costmap common params what should I use for the topic:
topic: mobile_base/sensors/bumper_pointcloud?

Also do I only work in static map or can I use it also with a dynamic map as in SLAM. If I can use it in dynamic map scenario then the rtabmap node will be set to mapping instead of localization and I need a global costmap params settings for dynamic map which I haven't found online.
How should I proceed from here?

Thank you

[matlabbe]

Hi,

for the time diff warning, can you can a flat 30 Hz on all topics with your computer? Which config do you use with D435i? I recommend to not use the RGB camera, but left IR + depth instead with IR emitter disabled. An example of that can be found on this page: RealSense D435i camera (IR-Depth)

For navigation, I'll suggest to look at the Turtblebot3 example instead as the outdoor stereo one is more a use case in slightly more complex context: http://wiki.ros.org/rtabmap_ros/Tutorials/MappingAndNavigationOnTurtlebot

The usual way that people uses a SLAM package is to create (teleop or exploration) a static map using SLAM mode then switch to localization-only during autonomous navigation when the roobt is actually doing tasks. To handle dynamic obstacles, you may use the local/global costmaps of move_base.

cheers,
Mathieu