Aircraft without ADS-B transponders do not broadcast their latitude/longitude, so FlightAware uses multilateration of 1090MHz Mode S
to determine the aircraft's location by using time difference of arrival (TDOA) when
an aircraft is detected across three or more receivers/ground stations. Using MLAT, FlightAware can take the aircraft's transponder-provided identification
and altitude, then determine the latitude/longitude, and provide real-time flight tracking.
Because an aircraft must be within line-of-sight of three or more FlightAware receivers, MLAT is currently available only in a limited coverage area at this time, unlike our
current ADS-B coverage. MLAT positions are effectively real-time, although calculation delays and processing latency is generally 4-6 seconds. FlightAware
currently emits up to six MLAT positions per minute per aircraft on the web site.
How it works
MLAT-enabled receivers keep the FlightAware server up to date on which Mode S aircraft are being received. When a particular aircraft is being received from three or more receivers,
the server requests sufficient Mode S data from the receiver to sync the time and multilaterate the position of the aircraft. An MLAT-enabled feeder will use approximately 50Kbps of
upstream bandwidth while actively contributing to MLAT flight tracking.
Improving Availability of MLAT flight tracks
Both PiAware (v2.0 and above) and FlightFeeder (v7.0 and above) ground stations can currently participate in MLAT
and support for additional hardware/software solutions is coming in late 2015. Deploying more receivers in an area will directly improve the ability
for FlightAware to generate MLAT positions. For optimal coverage, receivers should be 10-150km apart and in a triangular, square, or circular pattern -- not in a straight line like
along a road. Recruiting other people in your general area to host new PiAware or FlightFeeder sites is the best way to grow the availability of
FlightAware's MLAT network.
As of Friday, July 28, 2017, 8,941 receivers are connected and capable of producing MLAT data (view more receiver stats).
Multilateration (MLAT) flight tracking on FlightAware.com
When available, FlightAware's MLAT
positions of Mode S aircraft can be seen in the track log alongside regular RADAR, datalink, and projected positions.
MLAT flight tracking on PiAware
For people running PiAware and connecting directly to the PiAware web server, FlightAware
automatically feeds MLAT-derived positions to your PiAware web interface for live
MLAT tracking of Mode S aircraft that your receiver and antenna can see. MLAT aircraft are depicted on the map and the
chart in purple.
Multilateration (MLAT) Links