How to integrate loop closure?

[Mohamed Abdelkader Zahana]

Hi @WoosikLee2510
Is it possible to integrate loop closure with MINS. My goal is to use MONO VIO + loop closure.

Thanks

[Woosik Lee]

Hi, @mzahana.
You can use UpdaterVicon to fuse loop closure information to filter.
Say, your loop closure method in another thread detected loop closure and computed a constraint that can update the front end. You can convert the loop closure constraint to global pose information (like Vicon) with uncertainty (you may want to set a conservative value).

[Mohamed Abdelkader Zahana]

Thanks @WoosikLee2510
Can the ov_secondary be used to do the loop closure and feedback to MINS?

[Woosik Lee]

Note ov_secondary does not provide information to update the front end (e.g., OpenVINS). I think it can work if you create your own publisher to publish the loop closure information and use MINS to subscribe it as global pose information.

[Mohamed Abdelkader Zahana]

I see there is a topic published for the output odometry from the loop fusion node
https://github.com/rpng/ov_secondary/blob/c6b9e62a8bae453a230d024b4626906f62b5fb98/loop_fusion/launch/posegraph.launch#L27

Can this be fed to MINS?

[Woosik Lee]

Sure. you can add a subscriber that subscribes (under here) to the topic with type, convert the message to vicon type, and pass it. to system.
I would be careful not to make the information overconfident because the loop closure information may be highly correlated to MINS and thus can easily hurt consistency.

[Mohamed Abdelkader Zahana]

I thought MINS already subscribes to vicon ? no? @WoosikLee2510

[Woosik Lee]

No, it is not implemented because full global pose information (ViCON) is not something the estimator usually has access to.
In the case you do not want to implement the subscriber by yourself but have rosbag that has the pose information converted from loop closure, you can use/run ros_bag which directly reads the messages from the bag and passes to estimator.