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{{see also|tracking systems}}
==Introduction==
[[Lighthouse]] is a laser-based [[Inside-out tracking|inside-out]] [[positional tracking]] system developed by [[Valve]] for [[SteamVR]] and [[HTC Vive]]. It accurately tracks the position and orientation of the user's [[head-mounted Display]] and [[SteamVR Controllers|controllers]] in real time. Lighthouse enables the users to move anywhere and re-orient themselves in any position within the range of the [[SteamVR Base Stations]]. It is a key technology that enables [[SteamVR]] to create the first holodeck or full-room experience in [[Virtual Reality]].
For Lighthouse high-speed position tracking performance is down ENTIRELY to IMU performance. It wouldn't be possible at all without another absolute reference system (optical, magnetic or otherwise) but it's the IMU that's doing the grunt-work.
However, the IMU is even more important for the Lighthouse than the [[Constellation]]. Lighthouse is a scanning system: not only do you not know the positions of markers at the same point in time, you don't even get the X and Y positions at the same point in time: there is a 4ms delay (4 scans per 16ms) between each laser strike for each sensor. If a controller is moving at a modest 1ms-1 , then between laser strikes it's moved 4mm! While throwing a controller like a cricket ball is extremely ill advised, a 150mph throw (~150mph hand speed) is 45ms-1, or 180mm between scans. Using the IMU data allows you to update parts of the position (X or Y coords, or polar spherical coords relative to the basestation, depending on how Valve are doing their math) independently of each other.
==Tracking volume==
