Hi Wim,

thanks for your reply.

this message occurs whenever I call:

transform_listener.lookupTransform("base_footprint","map",ros::Time(0),
base_footprint);

and it occurs once.

I've tried the tool you suggested and it looks like everything is ok:

RESULTS: for /map to /base_footprint
Chain is: /map -> /base_footprint -> /odom_combined
Net delay     avg = 0.020768: max = 0.064

Frames:
Frame: /base_footprint published by /robot_pose_ekf Average Delay:
0.0260556 Max Delay: 0.035
Frame: /odom_combined published by /gmapping_node Average Delay:
-0.000230769 Max Delay: 0

All Broadcasters:
Node: /gmapping_node 21.7028 Hz, Average Delay: -0.000230769 Max Delay: 0
Node: /robot_pose_ekf 32.1429 Hz, Average Delay: 0.0260556 Max Delay: 0.035
Node: /robot_state_publisher 51.6129 Hz, Average Delay: 0.00096875 Max
Delay: 0.001


the only weird thing is, that in rviz the transform arrows shows like
this: /base_footprint -> /odom_combined -> /map

might this be a sign of some problem?

thanks very much,

Michal


> Michal,
>
> Is this a message you see once at startup, or is your listener spewing
> lots of these messages?
>
> A good tool to debug this problem is the tf_monitor: "rosrun tf
> tf_monitor map base_link"
>
>
> Wim
>
> On Thu, Jun 24, 2010 at 2:53 AM,  <Michal.Stolba@cis.strath.ac.uk> wrote:
>>
>>
>> Hi all,
>>
>> I'm trying to follow the tutorial on transform listener:
>>
>> http://www.ros.org/wiki/tf/Tutorials/Writing%20a%20tf%20listener%20(C%2B%2B)
>>
>> I'm trying to use it with simulated pr2 and gmapping to determine
>> location
>> of the robot relative to the map. What I'm getting is following message:
>>
>> [ERROR] 4546.007000467: Could not find a connection between '/map' and
>> '/base_footprint' because they are not part of the same tree.Tf has two
>> or
>> more unconnected trees. When trying to transform between /map and
>> /base_footprint.
>>
>> although, rviz shows the transforms and connections just fine, tf_echo
>> outputs the transforms as well and tf_view prints out just one tree
>> (attached).
>>
>> Any hints on what might be the problem would be very appreciated.
>>
>> Michal
>> _______________________________________________
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>> ros-users@code.ros.org
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>>
>>
>
>
>
> --
> --
> Wim Meeussen
> Willow Garage Inc.
> <http://www.willowgarage.com)
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