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ADS-B vs. ADS-R: Key Differences Explained

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This article breaks down the differences between ADS-B and ADS-R, two important technologies used in modern air traffic management. ADS stands for Automatic Dependent Surveillance-Broadcast.

What is ADS-B?

  • ADS-B uses satellite navigation systems (like GNSS or GPS) to determine an aircraft’s position. This position is then broadcast periodically. This makes tracking aircraft easier and helps prevent collisions.
  • The system provides accurate position data to Air Traffic Control (ATC) and other aircraft.

ADS-B system

  • GPS devices on the aircraft receive signals from GNSS satellites, pinpointing the aircraft’s location.
  • This location information, along with other data, is broadcast to ADS-B ground stations and nearby aircrafts in near real-time.
  • Besides location, ADS-B also transmits speed, altitude, and 30-40 other parameters to ground stations and Air Traffic Controllers (ATCs).
  • It also feeds data to aircraft tracking applications.

The FAA (Federal Aviation Administration) has approved two systems for ADS-B:

  • UAT (Universal Access Transceiver): Operates at 978 MHz.
  • Mode-S transponder: Operates at 1090 MHz.

What is ADS-R?

  • ADS-R stands for Automatic Dependent Surveillance Rebroadcast.
  • It takes position information received on the ground from UAT-equipped aircraft and rebroadcasts it on 1090 MHz.
  • Conversely, ADS-R rebroadcasts 1090MHz data to UAT users.
  • Working with TIS-B, ADS-R gives all ADS-B-equipped aircraft a comprehensive picture of traffic in the airspace and on airport surfaces.
  • ADS-R delivers traffic data within a 15 nautical mile radius, and 5000 feet above or below the receiving aircraft’s position.
  • TIS-B (Traffic Information Service-Broadcast): This air traffic advisory service provides the ground track, altitude, speed, and distance of aircraft that are in radar contact with controllers, within a 15 nm radius, and up to 3500 feet above or below the receiving aircraft’s position.

Benefits of ADS-B

Despite the cost, ADS-B offers significant advantages:

  • Improved Safety:
    • Provides radar-like IFR (Instrument Flight Rules) separation in areas where radar coverage is limited.
    • Enables more accurate search and rescue response.
    • Helps pilots avoid collisions with other aircraft.
    • Offers real-time cockpit weather and airspace display.