On Tue, Oct 26, 2010 at 11:10 PM, nickopen <nicholas.hillier@gmail.com> wrote:

Apologies if this is a repost - I had a search and a bit of a read but
couldn't easily solve my problem.

We have a robot with a number of different localisation systems. The aim is
that based on estimate covariances etc, the "best" one will be used with
some smoothing in the transition between references.

Unlike the standard "map->odom->base_link->stuff" set-up that is described
in the navigation tutorials, where you have a node publishing the
corrections to the odometry to give you the map, our set-up is more like a
multi-rooted tree:

map_GPS->base_link
map_INS->base_link
map_SLAM->base_link
odometry->base_link
etc, and finally, some transform that is the result of some voting or
filtering process:
map_fused->base_link

We want to be able to easily switch between how the world looks in each of
these frames by simply selecting any of the map_* frames as the fixed frame
in rviz and in other nodes.

It seems that tf doesn't let you have a set-up like this with multiple
roots. Any suggestions on how we should re-cast our problem to fit into the
tf framework?


The directionality of a tf edge doesn't actually matter for most things.  So one solution would be to just have all those map frames be children of base_link, or of odometry (which would allow the transforms to be published less often assuming odometry drifts fairly slowly).
- Bhaskara








 
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Bhaskara Marthi
Research Scientist
Willow Garage Inc.
650-475-2856