Where does the device anchor locate?

Hi,

My goal is to obtain the device location (6 DoF) of the Apple Vision Pro and I find a function that might satisfy my need:

final func queryDeviceAnchor(atTimestamp timestamp: TimeInterval) -> DeviceAnchor?

which returns a device anchor (containing the position and orientation of the headset).

However, I couldn't find any document specify where does the device anchor exactly locate on the headset. Does it locate at the midpoint between the user's eyes? Does it locate at the centroid of the six world facing tracking cameras?

It would be really helpful if someone can provide a local transformation matrix (similar to a camera extrinsic) from a visible rigid component (say the digital crown, top button, or the laser scanner) to the device anchor.

Thanks.