Which system relies on broadcasting GPS location periodically?

The system that relies on broadcasting GPS location periodically is ADS-B, which stands for Automatic Dependent Surveillance–Broadcast. ADS-B is an air traffic surveillance technology that allows aircraft to determine their position based on satellite navigation (in this case, GPS) and periodically broadcast that information along with other data such as velocity and altitude to air traffic control and other aircraft. This continuous stream of real-time data enhances situational awareness for pilots and air traffic controllers, contributing to increased safety and efficiency in airspace management.

In contrast, primary radar does not rely on GPS but instead detects reflections of transmitted radar signals off objects, like aircraft, allowing it to determine their location. Secondary radar systems, such as SSR (Secondary Surveillance Radar), depend on transponders on the aircraft that reply to a radar signal but do not broadcast GPS positions independently; they provide information based on interrogations from the ground. Flight Data Processing refers to the systems that handle flight plans and provide air traffic controllers with relevant information but does not directly involve the broadcasting of GPS data by aircraft. This distinction highlights why ADS-B is the correct answer as the system specifically designed to use periodic GPS location broadcasts.