The ADS-B systems is cooperative depending system it means that the ADS-B Ground station use only to detect and decoding the ADS-B out message.
My question is can we calculate the the aircraft range using TDOA.
Ex :
Aircraft transmitted: TOT : 29597.2407 s.
Ground station received: TOR : 29597.2420 s.
Range = ( TOR-TOT )* C = 183 Nm
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2$\begingroup$ It seems the last part of your question is missing $\endgroup$– DeltaLima ♦Commented Feb 4, 2023 at 17:32
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$\begingroup$ Thanks, I edited now $\endgroup$– SkyMavenCommented Feb 4, 2023 at 18:07
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3 Answers
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Yes, that is not only possible it is commonly used. If you receive a signal at one station you can use TDOA to define a half-shell of all possible locations where the transmitter might be; as you add more and more geographically distinct receivers you can narrow down the set of possible transmitter locations until you know precisely where the transmitter must be. This is the same way GPS and other satellite-based navigation systems work, except in reverse.
Further reading:
Multilateration.com: Multilateration
SKYbrary: Wide Area Multilateration (WAM)
FlightAware: Multilateration (MLAT) Overview
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$\begingroup$ So the aircraft transmitting via ADS-B ES message the timing of output message? Because I checked the raw message that the aircraft transmitted and I didn't find the TOT ( broadcast position time)!!! $\endgroup$– SkyMavenCommented Feb 4, 2023 at 18:58
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$\begingroup$ If the aircraft is broadcasting an ADS-B message with its own location, then that message is used instead of trying to calculate the location. Unlike ADS-B, which is broadcast, Mode S replies are only transmitted when requested (by a ground or airborne station) and are therefore relatively rare. My suspicion is that MLAT systems simply assume that the message seen by various stations is always the same message. See mode-s.org for more details. $\endgroup$ Commented Feb 5, 2023 at 0:35
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Can we calculate the range? Yes. MLAT, or multilateration, is triangulation with extra points. ICAO has a whitepaper on MLAT. Since internet-connected devices can easily sync their time, it's easy to compare the reception time at various receivers to solve for the location.
Common crowdsourced ADSB sites do this- for instance, flightaware, flightradar24, radarbox.
See also: Does 'RADAR' include MLAT or ADS-B, etc?
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As you've described, from an aircraft to one receiver, using a timestamp on the message? No. This would require that both the receiver and have their clocks synchronized extremely precisely. A single millisecond of error corresponds to a range error of 162 nautical miles!
Time difference of arrival (TDOA) is a different thing. It uses multiple stations and measures the time arrival at each station to determine the aircraft's location. Since it doesn't use a timestamp from the aircraft, it doesn't rely on the aircraft's clock being accurate.
