I'm running up against a wall in the form of tf's tree restrictions.
Namely, I'd like to have both gmapping and amcl running simultaneously (long
story), but both publish XXX => odom_combined (naturally, the parent frame
is param-configurable).  The problem is, that tf (apparently) does not allow
multiple parents (eg. it forces it to be a tree), and there doesn't seem to
be a way to flip the directionality of the transform (odom_combined =>
XXX).

I thought perhaps tf_remap or tf_prefix would fit the bill... but after a
few hours of experimentation, both approaches still end up in this same
problem.  I guess... what I'm really looking for is something akin to
topic_tools/mux only for tf topics.  Then I could just flip the mux when I
want one transform or another.

Has anyone found a good solution to this sort of problem?

~Travis Deyle
PhD student @ Georgia Tech's Healthcare Robotics Lab
Co-Founder www.Hizook.com -- Robotics News for Academics & Professionals