Rotation Prior Jacobians

[Christian Forster]

1) The rotation prior Jacobians are set to Identity:

https://bitbucket.org/gtborg/gtsam/src/bf99e7d930e174e5e53bb0731d7324228426dbfa/gtsam/slam/PoseRotationPrior.h?at=develop&fileviewer=file-view-default#PoseRotationPrior.h-80

However, I think they should be equal to the Logmap derivative.

2) Is there a plan to replace the PoseRotationPrior with the generic PriorFactor?

https://bitbucket.org/gtborg/gtsam/src/bf99e7d930e174e5e53bb0731d7324228426dbfa/gtsam/slam/PriorFactor.h?at=develop&fileviewer=file-view-default#PriorFactor.h-88

there is the same issue with the Jacobians.

However, if the errors are small, it probably doesn't make much of a difference..

best, christian