# Question about Apriltag Configuration

Source: https://forum.modalai.com/topic/255/question-about-apriltag-configuration
Category: General Questions (https://forum.modalai.com/category/2/general-questions)
Posted: 2021-05-23 09:22:42 UTC by shlee853
Replies: 1 · Views: 510

## shlee853 · 2021-05-23 09:22:42 UTC

Hi,

I want to get meanning of apriltag configuration as below.

            "fixed_apriltags":      [{                      
                    "tag_id":       0,                                 
                    "R_tag_to_fixed":       [[0, -1, 0], [1, 0, 0], [0, 0, 1]],
                    "T_tag_wrt_fixed":      [0, 0, 0]
                    }],                                
    

AprilTag Id:0
R_tag_to_fixed: is this rotation matrix from body coordinator to ApriTag 0? Could you please let me know meaning of matrix?
T_tag_wrt_fixed: is this XYZ offset from body coordinator to Apriltag 0? right?

## Reply by modaltb (ModalAI staff) · 2021-05-24 15:33:23 UTC

Hi @shlee853 ,

There's a pretty good tutorial from our Guru here: https://www.youtube.com/watch?v=0j7CjmDvluM

-Travis