What is ADS-B?
ADS-B stands for Automatic Dependent Surveillance-Broadcast (ADS-B). It is a system that tracks and broadcasts aircraft position and movement using satellite signals. The GPS-derived position and groundspeed of ADS-B-equipped aircraft is broadcast to air traffic control and other aircraft. The system may also be used to transmit weather and traffic information.
Automatic - No operator input is required.
Dependent - Depends on Global Positioning System (GPS) and/or other navigational systems for aircraft position and velocity information.
Surveillance - Provides 3-D position and identification of aircraft to ATC and other aircraft.
Broadcast - Broadcasts relevant information to anyone with suitable equipment.
How does ADS-B work?
First, we need to understand the difference between ADS-B Out and ADS-B In. ADS-B Out refers to an aircraft broadcasting its position and other information. ADS-B In refers to an aircraft receiving the broadcasts and other information from the ground network such as traffic and weather information.
ADS-B Out works by broadcasting information about an aircraft's GPS location, altitude, ground speed and other data to ground stations and other aircraft, once per second. Air traffic controllers and aircraft equipped with ADS-B In can immediately receive this information. This offers more precise tracking of aircraft compared to radar technology, which sweeps for position information every 5 to 12 seconds.
ADS-B In provides operators of properly equipped aircraft with weather and traffic position information delivered directly to the cockpit. ADS-B In-equipped aircraft have access to the graphical weather displays in the cockpit as well as text-based advisories, including Notices to Airmen and significant weather activity.
(Refer to FAA AC 90-114B for more information)