Every Plane Is Now Visible: How ADS-B Ended Radar’s 80-Year Reign

On January 1, 2020, a fundamental change occurred in American skies. Every aircraft flying above 10,000 feet was required to broadcast its position, altitude, and velocity via Automatic Dependent Surveillance-Broadcast (ADS-B). After 80 years of radar dominance, aviation surveillance entered a new era – one where every airplane effectively announces its presence to the world.

The Radar Era

Since World War II, radar has been the backbone of air traffic control. Ground-based stations send out radio pulses that bounce off aircraft, revealing their positions to controllers. The technology works, but it has significant limitations:

• Coverage gaps: Radar can’t see over mountains, across oceans, or in remote areas
• Limited accuracy: Position updates come every 4-12 seconds with accuracy measured in miles
• Infrastructure cost: Each radar installation costs millions to build and maintain
• No intent information: Radar shows where aircraft are, not where they’re going
• Weather interference: Heavy precipitation can block or distort radar returns

These limitations forced conservative separation standards. Aircraft had to stay miles apart because controllers couldn’t be certain of exact positions.

ADS-B: A Different Approach

ADS-B flips the surveillance model. Instead of ground stations detecting aircraft, aircraft broadcast their own positions. The “A” stands for Automatic – transmissions happen continuously without pilot or controller action. The “D” means Dependent – the system depends on onboard GPS for position data.

Every second, an ADS-B-equipped aircraft broadcasts:

• Precise GPS position (latitude, longitude, altitude)
• Aircraft identification (callsign)
• Ground speed and heading
• Vertical rate (climbing, descending, level)
• Aircraft category (small, large, rotorcraft, etc.)

This information goes to ground stations that relay it to controllers, and simultaneously to other equipped aircraft that can “see” nearby traffic directly.

Accuracy and Coverage Transformation

The improvement over radar is dramatic:

• Position accuracy: GPS provides position accurate to meters, not miles
• Update rate: Once per second versus every 4-12 seconds for radar
• Coverage: Works anywhere with GPS signal, including over oceans and in remote areas
• No blind spots: Mountains and terrain don’t block GPS broadcasts
• Lower infrastructure cost: Ground stations are simpler and cheaper than radar

Benefits for Controllers and Airlines

ADS-B enables capabilities that were impossible with radar:

Reduced separation: With more accurate position data, aircraft can safely fly closer together. This means more aircraft in the same airspace – critical for congested regions.

Oceanic surveillance: For the first time, controllers can track aircraft across the Pacific and Atlantic with the same precision as domestic airspace. This enables more efficient routing and fuel savings.

Surface surveillance: ADS-B tracks aircraft and equipped vehicles on airport surfaces, preventing runway incursions.

Search and rescue: If an aircraft goes down, its last known position is accurate to meters, not miles – dramatically improving rescue response.

ADS-B In: Pilots See Traffic

While ADS-B Out (transmitting) is mandatory, ADS-B In (receiving) offers additional benefits. Equipped aircraft can display nearby traffic on cockpit displays, giving pilots situational awareness previously available only to controllers.

The display shows:

• Relative position of nearby aircraft
• Altitude and whether they’re climbing or descending
• Potential conflicts highlighted in warning colors
• Traffic advisories from the system

This information supplements Traffic Collision Avoidance System (TCAS) advisories and gives pilots a complete picture of their traffic environment.

Weather and Airspace Information

In the United States, ADS-B ground stations broadcast weather and airspace information back to aircraft through a service called FIS-B (Flight Information Services-Broadcast). Pilots receive:

• NEXRAD weather radar imagery
• METARs and TAFs (current and forecast weather)
• NOTAMs (notices to airmen)
• Temporary flight restrictions

This free service has been transformative for general aviation pilots who previously relied on expensive satellite weather subscriptions.

Security Considerations

ADS-B’s openness has raised security discussions. Unlike radar, which requires specialized equipment to interpret, ADS-B broadcasts can be received by anyone with a cheap software-defined radio. Websites like Flightradar24 and FlightAware display real-time aircraft positions worldwide using ADS-B data.

This transparency has benefits – families can track flights, and accident investigators have instant access to flight data. But it also means aircraft positions are public information, which has implications for military and government operations.

The End of Radar?

Radar won’t disappear immediately – it remains important for detecting non-equipped aircraft and as a backup system. But new radar installations are increasingly rare, and the long-term future clearly belongs to ADS-B and its successors.

The transition represents one of aviation’s most significant infrastructure changes. What took eight decades to build – a global network of radar stations – is being supplemented and eventually replaced by a system where every aircraft simply tells the world where it is. It’s simpler, cheaper, more accurate, and more capable. The radar era isn’t quite over, but its end is now clearly in sight.