Explain about sensor frame

[NguyenDuyDuc]

Hi,

I am doing debug_case5 package.

I read that the answer of laser_link is summit_xl_a_front_laser_link.
My question is why is it summit_xl_a_front_laser_base_link?

And in practical, when I see the tf_tree, which one I will choose summit_xl_a_front_laser_link or summit_xl_a_front_laser_base_link?

Thanks

[rtellez]

That is a very good question @NguyenDuyDuc !

If you check in Rviz, you can see that for whatever the reason, there are two frames in the robot that are named something about laser:

• summit_xl_a_front_laser_link
• summit_xl_a_front_laser_base_link

So which one should we use? (that is your question)

The answer is… it depends. It depends on what are you doing with that information.
In the exercise, you are using the laser data. Hence, you need to reference the laser data to the frame of the sensor that is publishing it, not the other frame.

so how do you find which one is the frame in which the laser is publishing the data related to? By checking one laser message, which contains the info of the frame used:

So as you can see in the picture, the laser is publishing laser data in the summit_xl_a_front_laser_link frame and that is why you should use that one.

For a different robot, you should follow the procedure I explained here to figure out which is the correct frame.