Coordinate system for pose priors

[torjusti]

Hi,

I'm trying to use the "Add prior" button in the database viewer to "hard code" the position of a pose in an attempt to correct the map a bit.

However I find that the feature gives much larger distortions than I would expect. In fact accepting the pre-filled pose (equal to the odometry pose) bends the graph a lot.

Graph before adding any priors:

I then add a prior that is literally equal to the odometry pose, which I would expect to do nothing to the map:

However this changes the map a lot:

Am I misunderstanding how this feature works?

[matlabbe]

I think there is a bug when both gravity and prior constraints are on the same node at the same time. I'll need more time to check in depth.

But normally, the priors are like "anchors" for the graph optimization and would deform the graph to match these poses.

[torjusti]

This seems to be working again following commit #b9d7e80

Thanks a bunch for your work :)