What is the purpose of ADS-B for aircraft position surveillance?

The purpose of ADS-B (Automatic Dependent Surveillance–Broadcast) for aircraft position surveillance is to use satellite navigation to determine an aircraft's position. This technology relies on Global Navigation Satellite Systems (GNSS), such as GPS, which allows aircraft to determine their exact location in real-time with high accuracy. Once the aircraft's position is determined, it broadcasts its location along with other pertinent information, such as velocity and aircraft identification, to nearby aircraft and ground stations. This enhances situational awareness and contributes to safer and more efficient airspace management.

In contrast, some of the other options suggest methods of position determination that are not applicable to ADS-B. For example, radar does not play a part in ADS-B; this system is independent of traditional radar technology. Likewise, ADS-B does not require direct communication between aircraft; the position information is broadcasted and received automatically without a need for direct interaction. Lastly, calculating position based on visual contact is not a viable method for surveillance in air traffic management, as it relies on human perception rather than automated satellite-based systems.