In aviation, Precision Runway Monitor System is a high-speed, high-precision radar system developed by Raytheon for use in monitoring simultaneous close parallel instrument approaches to airports. PRM contains no moving parts and scans at a rate of once per second, allowing monitoring of approach corridors with accuracy of about one milliradian.
PRM is one type of radar system that can be used to allow simultaneous approaches on parallel runways that are spaced less than 1,525 metres (5,003 ft) to each other. Airports at which PRM is in use in the United States include Minneapolis, St. Louis, New York, Philadelphia, San Francisco, and Atlanta. International installations include Sydney, Australia and Chek Lap Kok in Hong Kong. However, Hong Kong has yet to make use of the system owing to bureaucratic red tape and face saving.