Anchor nodes for multi-robot SLAM?

[Maurice Fallon]

Hi Folks,

I'm wondering if multi-robot or multi-session SLAM is supported with GTSAM.

Michael Kaess describes anchor nodes as a means to do this in his old version of iSAM here:

https://people.csail.mit.edu/kaess/isam/doc/Tutorial.html

Does anyone know if this concept exists in GTSAM?

best wishes,

- Maurice

[Frank Dellaert]

No, not out of the box.

[Maurice Fallon]

Thanks for the reply Frank.

For any readers interested in doing similar, some notes:

I was able to implement a multi-session SLAM system by keeping track of the pose graph constraints of the individual sessions outside of the GTSAM solver.

When a loop closure was established between two different sessions (a primary and a secondary session), the trick was to use that loop closure relative transformation to transform the initial guess for the secondary session nodes into the fixed frame of the primary mission.

Then after that, subsequent inter-session loop closures could be inserted into the iSAM solver - as in the single session case. In particular, the usual iSAM2 LM solver was stable and reliable.

I didn't feel the need for explicit support for multi-session SLAM was needed.

bw,

- Maurice

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[Dellaert, Frank]

Cool! Example would make for a colab notebook :-) PS colab is my goto for prototyping with GTSAM now. `!pip install gtsam` and off to the races :-)

Frank

---

From: gtsam...@googlegroups.com <gtsam...@googlegroups.com> on behalf of Maurice Fallon <mauric...@gmail.com>
Sent: Friday, November 19, 2021 2:30:55 AM
To: Frank Dellaert <dell...@gmail.com>
Cc: gtsam users <gtsam...@googlegroups.com>
Subject: Re: [GTSAM] Re: Anchor nodes for multi-robot SLAM?

 

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[Nicolas Perez]

Hi Maurice,

If you were willing to upload an example of multi-session SLAM using GTSAM to GTSAM's Github page, that would be awesome! I'm sure many people would benefit. There is a directory specifically for examples: https://github.com/borglab/gtsam/tree/develop/examples 

[Maurice Fallon]

This goes way back into the GTSAM group archives, but this request is answered here by Giseop Kim (of ScanContext fame):

https://github.com/gisbi-kim/multi-robot-isam-example

bw,

Maurice