# Possible Mistake on Unit 1 Notes

**URL:** <https://get-help.theconstruct.ai/t/possible-mistake-on-unit-1-notes/26999>\
**Category:** TF ROS 101\
**Tags:** error\
**Created:** [October 24, 2023, 1:14pm UTC](https://get-help.theconstruct.ai/t/possible-mistake-on-unit-1-notes/26999 "2023-10-24T13:14:22Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![ACTISA2](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/a/f05b48/32.png) [@ACTISA2](https://get-help.theconstruct.ai/u/ACTISA2)\
**Post date:** [October 24, 2023, 1:14pm UTC](https://get-help.theconstruct.ai/t/possible-mistake-on-unit-1-notes/26999/1 "2023-10-24T13:14:22Z")

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Hello, just wanted to inform that at the end of Exercise 2.1 there’s this comment: As you can see, all three frames corresponding to **the 3D turtle, the iRobot, and the Coke\_can** now appear in the TF Tree.

This is incorrect since by this time, we have just made the tf broadcast of turtle1 and turtle2 frames. So we can only see world, turtle1 and turtle2 (turtle1 being above world, since it seems the turtle is on the origin of Gazebo). Coke can seems to be the next exercise.

Just wanted to point this out if you want to correct it.

Best regards,  
ÁngelLoGa

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**Author:** ![ralves](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/ralves/32/7039_2.png) [@ralves](https://get-help.theconstruct.ai/u/ralves)\
**Post date:** [October 25, 2023, 12:49pm UTC](https://get-help.theconstruct.ai/t/possible-mistake-on-unit-1-notes/26999/2 "2023-10-25T12:49:18Z")

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Hi @ACTISA2,

thank you very much for pointing this out.

I already took notes of the errors you reported, and the correct text will soon be available.

Once again, thank you very much for helping us identify this mistake.

**#KeepPushingYourROSLearning**

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**Author:** ![system](https://get-help.theconstruct.ai/uploads/default/original/2X/9/9d3ce8305cc0d0d9b6e07d15767a6f245c526f1b.jpeg) [@system](https://get-help.theconstruct.ai/u/system)\
**Post date:** [October 30, 2023, 12:49pm UTC](https://get-help.theconstruct.ai/t/possible-mistake-on-unit-1-notes/26999/3 "2023-10-30T12:49:25Z")

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