# Re3 ros2 check head calibration

**URL:** <https://forum.hello-robot.com/t/re3-ros2-check-head-calibration/963>\
**Category:** Ask\
**Created:** [April 28, 2024, 12:30am UTC](https://forum.hello-robot.com/t/re3-ros2-check-head-calibration/963 "2024-04-28T00:30:47Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Peiqi\_Liu](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.hello-robot.com/peiqi_liu/32/536_2.png) [@Peiqi\_Liu](https://forum.hello-robot.com/u/Peiqi_Liu)\
**Post date:** [April 28, 2024, 12:30am UTC](https://forum.hello-robot.com/t/re3-ros2-check-head-calibration/963/1 "2024-04-28T00:30:47Z")

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Hello I am currently following [this instruction](https://github.com/hello-robot/stretch_ros2/tree/humble/stretch_calibration) to check my re3 robot’s head calibration. However, when running this command

> ros2 run stretch\_calibration check\_head\_calibration

I did not see any calibration errors output by the process. This was unlike checking head calibration on re1 and re2. Do you have any ideas what happened? Attached is what I see on the screen. I suspect this has something to do with rviz2.

 ![1714263424788](https://canada1.discourse-cdn.com/flex030/uploads/hello_robot2/original/1X/0e1d7f6fac64a8d5c69a6bcd5664b7b706177870.jpeg)

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**Author:** ![bshah](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.hello-robot.com/bshah/32/55_2.png) [@bshah](https://forum.hello-robot.com/u/bshah)\
**Post date:** [May 1, 2024, 2:09am UTC](https://forum.hello-robot.com/t/re3-ros2-check-head-calibration/963/2 "2024-05-01T02:09:39Z")

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Hi @Peiqi_Liu, you can safely ignore the step that asks you to run `ros2 run stretch_calibration check_head_calibration`. That documentation is a bit out-of-date, and I plan to update it shortly to remove the step.

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**Author:** ![Peiqi\_Liu](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.hello-robot.com/peiqi_liu/32/536_2.png) [@Peiqi\_Liu](https://forum.hello-robot.com/u/Peiqi_Liu)\
**Post date:** [May 1, 2024, 3:45am UTC](https://forum.hello-robot.com/t/re3-ros2-check-head-calibration/963/3 "2024-05-01T03:45:04Z")

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But how can I check whether current calibration is accurate enough?

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<div class="post-metadata">

**Author:** ![bshah](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.hello-robot.com/bshah/32/55_2.png) [@bshah](https://forum.hello-robot.com/u/bshah)\
**Post date:** [May 1, 2024, 5:11am UTC](https://forum.hello-robot.com/t/re3-ros2-check-head-calibration/963/4 "2024-05-01T05:11:55Z")

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When you get to step 4 in “Calibrate Stretch”, you will run `ros2 launch stretch_calibration process_head_calibration_data.launch.py`, and you’ll see an optimization printing out to the terminal. When it exits, you’ll see a final error term (typ. \<0.03).

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<div class="post-metadata">

**Author:** ![Peiqi\_Liu](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.hello-robot.com/peiqi_liu/32/536_2.png) [@Peiqi\_Liu](https://forum.hello-robot.com/u/Peiqi_Liu)\
**Post date:** [May 1, 2024, 5:25am UTC](https://forum.hello-robot.com/t/re3-ros2-check-head-calibration/963/5 "2024-05-01T05:25:44Z")

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Got it,  
but does that mean that I have to calibrate the robot before I can check the errors?

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**Author:** ![bshah](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.hello-robot.com/bshah/32/55_2.png) [@bshah](https://forum.hello-robot.com/u/bshah)\
**Post date:** [May 1, 2024, 4:16pm UTC](https://forum.hello-robot.com/t/re3-ros2-check-head-calibration/963/6 "2024-05-01T16:16:21Z")

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Yes, performing a fresh URDF calibration is a good workaround while we update the docs/tools for the checking calibration section.