Question about Oculus rift VR headset positioning with Unity

Hi there,

I am developing a scene in unity for a meta rift S headset and I am just wondering about how does the positioning and coordinate system work within the unity scene once I put on the VR headset as the headset and unity have different coordinate systems.

I am assuming once I am in the unity scene, everything for the VR would be in terms of the unity coordinates (so the headset's positioning system would follow the scene, please advise if this is not the case) but where would be the origin (0,0) of the scene in headset? And is there anyway I can extract the raw data of the x, y, z, and possibly the quaternions of the controllers and the headsets while using the headset? I want to use these position data and send it to a device in the real world through ROS.

Thanks for any help and advise in advance!