  Immersiveness is the main characteristic of Virtual Reality(VR) applications.
Precise integration between hardware design and software are necessary for
providing a seamless virtual experience. Allowing the user to navigate the VR
scene using locomotion techniques is crucial for making such experiences
`immersive'. Locomotion in VR acts as a motion tracking unit for the user and
simulates their movement in the virtual scene. These movements are commonly
rotational, axial or translational based on the Degree-of-Freedom (DOF) of the
application. To support effective locomotion, one of the primary challenges for
VR practitioners is to transform their hardware from 3-DOF to 6-DOF or vice
versa. We conducted a systematic review on different motion tracking methods
employed in the Head-Mounted-Devices (HMD) to understand such hardware
transformation. Our review discusses the fundamental aspects of the
hardware-based transformation of HMDs to conduct virtual locomotion. Our
observations led us to formulate a taxonomy of the tracking methods based on
system design, which can eventually be used for the hardware transformation of
HMDs. Our study also captures different metrics that VR practitioners use to
evaluate the hardware based on the context, performance, and significance of
its usage.
