Automatic Dependent Surveillance (ADS)

From: (Ralph N. Smith)
Organization: Mitre Corporation, McLean, VA
Date:         11 Dec 92 17:42:31 PST
References:   1 2 3
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In article <airliners.1992.135@ohare.Chicago.COM> (Harry Funk) writes:
>In article <airliners.1992.116@ohare.Chicago.COM> (Duane F Marble) writes:
>>A small point with respect to the material quoted from the New
>>Scientist: Global Positioning System (GPS) birds do not "observe"
>>anything, they just permit a ground based unit to compute it's
>My guess is that he was referring to Automatic Dependent Surveillance (ADS)
>systems based on SATCOM, which has even less to to with GPS/Glonass birds.
>The planes [would] communicate their positions by means of a satellite link
>to a ground-based tracking/control system.  United currently has a few
>747-400's that are so equipped.  The major benefit envisioned is for
>oceanic routes, where the fixed spacing (slots) system currently used
>results in suboptimal tracks for a number of users of the system.  ADS is
>the successor to the Oceanic Display and Planning System (ODAPS), which I
>think is currently installed at the Oakland and NY Air Route Traffic
>Control Centers (ARTCCs).  

A few clarifying remarks about ADS.  Technically, what United is currently
doing in the Pacific is position reporting, where the aircraft sends a
given set of information to the ground at fixed intervals.  ADS systems
involve more ground interaction, with the ground-based systems
specifying the types of information desired, and the circumstances under
which that information is provided, either periodically or at the
occurrence of certain events in a flight.

Also, there needs to be a differentiation made between the service
provided by the aircraft, in this case ADS, and the communications by
which the information is being sent.  With a proper communications
infrastructure, ADS and other air-ground communications based
applications, can run without being concerned which particular
air-ground data link is carrying the data, whether it be satellite, VHF
radio, or any of a variety of communications links.  ADS can also be
used to retrieve intent information from an aircraft, in addition to
current status information.

Work is currently under way to integrate ADS reporting into the ODAPS
system, rather than replacing it, at least in the near term.  Also, an
ADS-based application is one of the products to be produced by the
Aeronautical Telecommunication Network (ATN) Project (ATNP).  Several
organizations in the aviation community are involved in the ATNP,
including airlines (United is among them), avionics manufacturers, and
the FAA.

The potential benefits of ADS are substantial, including increased
safety, and substantial savings in fuel and flight time.

Ralph N. Smith
The MITRE Corporation				(703)883-6084
McLean, Virginia

All views and opinions are my own, so don't try to hold my employer