AprilTag and its Homography Matrix

Hey guys, I am currently using AprilTag’s in my project in ROS2 and everything works fine.

The only things I still struggle with, is the data, which I get from the detection’s of the AprilTag.

I am using this package here:

When everything is set up and works fine, I can subscribe to the /apriltag/detections Topic and get all the data from the AprilTag.
One part of the data, is the Homography Matrix with its 9 components and they are changing always, when I move the AprilTag, why is it like that?

As far as I have understood, the Homography give me the relation between the projection of the 3D Pose of the AprilTag into the 2D image plane, right? But why does they change all the time? Does the projection from 3D to 2D not depend on my camera calibration data, which gets published on the /camera_info Topic of my camera node (In my case it is v4l2)

I would really appreciate it, when someone could clear stuff up for me. =)

PS: Sorry if I am completely of the tracks on this Forum, but on the ROS Forums most people have little knowledge of Computer Vision, so I would appreciate it, if here its the place to be =)

Have a look at:

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Thank you very much!

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