Traffic information service – broadcast
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Traffic information service – broadcast (TIS–B) is an aviation information service that allows pilots to see near real time positions and ground track in 45 degree increments of other nearby aircraft as either a "traffic advisory" or "proximate" intruder, for the purposes of collision avoidance. It presents to the pilot a combined representation of aircraft positions derived from GPS satellite and ground-based radar data, specifically: aircraft's replies to ATC interrogations (i.e., they are responses to queries as sent to the aircraft from air traffic controller on the ground).
TIS-B is broadcast to aircraft using both the 1090 MHz extended squitter (1090 ES) and the universal access transceiver (UAT) band of automatic dependent surveillance-broadcast (ADS-B). Currently the service mainly benefits general aviation (GA) aircraft equipped with ADS-B "in" hardware by providing a traffic information relay to a screen in the cockpit. In order to use TIS, the client and any intruder aircraft must be equipped with the appropriate cockpit equipment and fly within the radar coverage of a Mode S radar capable of providing TIS. Typically, this will be within 55 NM of these sites.
At this time TIS–B is meant to be only a supplement to visual separation from other aircraft when operating in visual meteorological conditions (VMC) and as a backup to radar, which in remote areas only updates every 13 seconds, when operating under instrument flight rules (IFR).