Magnetic data is the term used for data that is acquired from magnetic (as opposed to optical) motion capture systems. With magnetic systems a central magnet is used to create a field in which sensors can determine their position and orientation as they move about in the field. Raw magnetic data has no hierarchy information, the sensors do not know where they are relative to the other sensors, only where they are in the magnetic field. The file formats for magnetic motion capture data reflect this, in this respect they are somewhat similar to the BVA file format.