Localize multiple robots with a single map database

[aamirhatim]

As the title says, I would like to use a single map database to localize multiple robots via ROS. Here is my setup:

- Four identical mobile robots, each with a stereo camera mounted in the same place
- An existing map built with rtabmap_ros using one of the robots
- A remote machine running rosmaster

Assuming all networking between machines is handled, is there a way that I can serve the map database on the remote machine and have each robot use it to localize itself within the map? I am trying not to load the database on each robot.

Thank you!

[matlabbe]

Hi,

Maybe not exactly what you want, but it is possible to launch many rtabmap nodes in localization mode with the same database (see this example https://github.com/introlab/rtabmap_ros/blob/master/launch/tests/test_two_kinects_one_map.launch). In your setup, the 4 rtabmap would have to be started on your ros master in different namespaces as rtabmap needs to load a local database file.

cheers,
Mathieu

[ekuruvilla]

Hello Mathieu,

When the same database is shared among multiple rtabmaps, is there any risk of more than one rtabmap simultaneously modifying the database and corrupting it?

Thanks,
Eapen

[aamirhatim]

I ended up running the setup that Mathieu described earlier and did not run into any corruption issues but the instances were all in localization mode. I will mention though that it seemed like moving the database file to a different location resulted in some kind of corruption and I would need to build a new db. This is more anecdotal however and I wasn't able to do more targeted testing on this.

Btw, thank you Mathieu for the suggestion - it worked well for my use case :)

[ekuruvilla]

Thank you aamirhatim for the confirmation that this approach works.  I see that corelib/src/DBDriver.cpp uses MUTEX when accessing the database and thereby making the databases changes thread safe.