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Missing connection between /map and /base_link

asked 2013-04-29 07:01:07 -0500

mharms gravatar image

updated 2013-05-02 04:52:55 -0500

Hi at all,

I am very new to ROS. After working out the tutorials and the Book "ROS by example" I got the following error, when running rviz with my personal robot.model:

> Waiting on transform from /base_link to /map to become available before running costmap, tf error: Could not find a connection between '/map' and '/base_link' because they are not part of the same tree.Tf has two or more unconnected trees. <<<

In my urdf File I have got only base and a link to a Laser_link, which is not used yet.

I looked through many files comparing mine with the turtlebot-files. I dont understand where the link between base_link and map is made, I believe it is in the move_base but I really dont know. If it helps I can send the content of files but dont know which one.

Hope that someone here can help me.

Thanks and best wishes

Michael, Berlin, Germany

EDIT

Sorry for asking again. I get the error in the console when running roslaunch myrobot fake_turtlebot.launch, not in rviz, si the error message doesnt depend on my settings in rviz. I do this too find out and compare my file with turtlebot-tutorial, why my robot isnt operating correct, eg. when I want to run move_base and click in the map to define a goal. When I run myrobot myrobot.lauch the rviz shows the thin blue line as path to the goal correctly, but is moving somewhere in the wrong direction with flashing the red lines.

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answered 2013-04-29 08:36:14 -0500

rohan gravatar image

updated 2013-04-29 08:37:03 -0500

In RViz in the global options you can choose fixed frame. Is it map? Try choosing "base_link" as your fixed frame. You can have a look at the image below and that is my robot model in rviz.

https://portal.bitcasa.com/send/bbb86466824c8ef50a8b4c01f34bd3fde55d50a9c1bf27c9588f4350e7039ee9/39b88c7ecd95c50b44c0d3fc722d96a1dba01e2989a07e4c32586c9fdfd1986a (link text)

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Thank you very much, for your rapid help and the provided image. Yes, it is set to /map. I will try changing this tomorrow when I am back to my work.

mharms gravatar image mharms  ( 2013-04-29 09:49:35 -0500 )edit
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answered 2013-04-29 15:18:30 -0500

weiin gravatar image

Take a look at http://ros.org/reps/rep-0105.html#coordinate-frames to understand the various frames used.

Use rosrun tf tf_monitor or rosrun tf view_frames to see if the required frames are being broadcast.

In general, the /map (to /odom or /base_link) frame is broadcast by a localization node (eg. amcl or gmapping). The /odom (to /base_link) frame is broadcast by an odometry producing node (eg. from your wheel encoders or robot_pose_ekf).

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Asked: 2013-04-29 07:01:07 -0500

Seen: 8,788 times

Last updated: May 02 '13