This paper is a survey of position-tracking technologies and their use in virtual reality (VR) applications. A framework is established to evaluate the suitability of a position-tracking implementation for virtual reality use. Mechanical, optical, magnetic, and acoustic implementations are discussed with examples of each. Also, the effect of position tracking on a virtual reality user is discussed, especially with regard to the position tracker's role as a cause of simulation sickness. A catalog of implementations and uses is included in an appendix.