Hi Sabrina,
Could you check some of the debugging outputs from tf.  There are debugging
methods here:  http://www.ros.org/wiki/tf/Debugging%20tools  Of particular
interest is the output of view_frames.

Also, are you running in simulation?  If so do you have /using_sim_time set
to true?  This can cause a race condition at startup and cause the "no
common time" error.  See documentation here http://www.ros.org/wiki/Clock

Tully

On Fri, Apr 16, 2010 at 2:51 AM, <sabrinakliegl@innok.de> wrote:

>
> Hi everybody,
>
> I get a strange error when I try to do a transformPose:
> [ERROR] ... Could not find a common time /base_link and /map
> and
> [ERROR] ... Could not find a connection between /base_link and /map
> because they are not part of the same tree.
>
> But when I start tf_echo /base_link /map there is a proper transformation.
>
> The error occurred suddenly when I started a launch-file which did
> work without any problem at the last startup.
>
> 'rosrun tf reset_time.py' solves the problem for a short time, but
> after some successful calls of "transformPose" the error is back again.
>
> Any ideas?
>
> Greetings from the RoboCup German Open in Magdeburg,
> Sabrina
>
>
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>



-- 
Tully Foote
Systems Engineer
Willow Garage, Inc.
tfoote@willowgarage.com
(650) 475-2827