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ADS-B Technology Overview
Marc Ramsey
PASCO Safety Seminar
Oakland, California
November 4, 2006
Topics• What is ADS-B?• How Does ADS-B Work?• Why Ground Stations?• Broadcast Services• Current Continental US ADS-B Coverage• Expanded Coverage: 2008 to 2010?• Universal Access Transceivers• Will ADS-B Replace Transponders?• Why Should We Care?• What Can We Do?
What is ADS-B?
• Automatic– Periodically transmits information with no pilot or
operator input
• Dependent– Position and velocity data derived from Global
Positioning System (GPS)
• Surveillance– Determines position of aircraft, vehicles, or ground
obstructions
• Broadcast– Transmitted data available to anyone with
appropriate receiving equipment
How Does ADS-B Work?
• ADS-B transmitter periodically transmit:– Unique identifier– 3D Position and velocity vector from GPS
• Altitude from pressure sensor and/or GPS
• ADS-B receiver receives:– Data from nearby ADS-B transmitters– Traffic and weather data from ground stations
• ADS-B transceiver transmits and receives• Two types of ADS-B devices
– Mode S/ES (Extended Squitter) at 1090 MHz– UAT (Universal Access Transceiver) at 978 MHz
• Intended for General Aviation use
Why Ground Stations?
• Receive position/velocity data from ADS-B (both UAT and S/ES) equipped aircraft
• Pass received data to ATC system• Obtain traffic data from ATC system for other
ADS-B and transponder equipped aircraft• Broadcast composite traffic data• Broadcast weather and airspace data• Each station has a range of 100 to 150 miles
Who Can See Who?
ADS-B UAT ADS-B ES Mode A/C/S
ADS-B UAT IN YES via GS via GS
ADS-B ES IN via GS YES via GS
TCAS NO Maybe YES
ATC via GS via SSR/GS via SSR
–GS Ground Station–SSR Secondary Surveillance Radar
Broadcast Services: TIS-B
• Traffic Information Service• Provides real-time position reports
– ADS-B equipped aircraft– Mode B/C equipped aircraft from secondary surveillance
radar data
Broadcast Services: FIS-B• Flight Information Service• National Weather Service products
– NEXRAD
• Special use airspace– Temporary flight restrictions (TFRs)
Universal Access Transceiver
• Transmits current state vector (3D position/velocity) once per second
• Receives TIS-B and FIS-B• Low transmit power requirements
– Low power (limited to 18,000 feet) 7 to 18 watts– Medium power (no alt. Restriction) 16 to 40 watts– Short transmit duty cycle (0.03%)
• Garmin GDL 90– Only UAT currently certified– $8000 without display– $16,500 with color display
Will ADS-B Replace Transponders?
• Short answer: eventually…– Most air transport aircraft equipped by 2020– Most other aircraft equipped by 2030
• Advantages– Precise position data on all aircraft in ATC system– UAT transceivers will eventually be smaller,
lighter, and use less current than Mode C– ADS-B ground stations less expensive and cover
wider area than primary/secondary radar systems
• What’s holding it up?– Lack of integration with TCAS– Lack of ground stations
Why Should We Care?
• Potential benefits– Allow gliders, paragliders, hangliders, etc. to be
fully integrated into future ATC system– Ultimately much lower power requirements than
existing Mode C or S transponders– Integrated collision avoidance– Real-time glider tracking for contests, etc.
• Potential Issues– Short term lack of suitable units– Competition
• UAT equipped gliders can be tracked by competitors • Weather data available to UAT equipped competitors
What Can We Do?
• Push for short term installation of ground station in Reno area
• Propose pilot program involving subsidized installation of UATs in Reno area gliders
• Ask for waiver allowing occasional use of low power UATs in wave windows
• Can we interest someone in developing low cost, low power UAT using PDA as display?
• Other ideas?