ADS-B Tracker: How Aircraft Surveillance Technology Works for Everyone

ADS-B tracker discussions have gotten complicated with all the “why can you track commercial flights on a website but not military or some private planes” debates, the ADS-B versus traditional radar comparisons, and “how does a $25 USB dongle connected to a Raspberry Pi actually see the same aircraft that air traffic control is tracking” conversations flying around. As someone who has spent years following aviation surveillance technology and the specific technical architecture that makes modern aircraft tracking both remarkably transparent and selectively opaque depending on who operates the aircraft, I learned everything there is to know about ADS-B tracking. Today, I will share it all with you.

But what is ADS-B, really? In essence, it’s Automatic Dependent Surveillance-Broadcast — a surveillance technology where aircraft continuously broadcast their GPS-derived position, speed, altitude, and identification to any receiver within range, replacing the older paradigm of ground-based radar interrogating each aircraft individually with a system where aircraft proactively announce their own position using GPS rather than waiting to be detected. But it’s much more than a flight tracker. For air traffic controllers, pilots, and the millions of aviation enthusiasts who use consumer flight tracking services, ADS-B represents a fundamental change in the transparency of airspace — one that has made air traffic patterns visible to anyone with a receiver, while simultaneously creating privacy debates about which aircraft should be exempt from that visibility.

How ADS-B Actually Works

An aircraft equipped with ADS-B Out broadcasts a message approximately twice per second on 1090 MHz (for transport category aircraft and most general aviation) or 978 MHz (for general aviation operating below 18,000 feet in the U.S., using Universal Access Transceiver — UAT). This message contains the aircraft’s GPS position, GPS-derived altitude, groundspeed, track, and transponder code. Any ADS-B receiver in range — whether an FAA ground station, an aircraft with ADS-B In capability, or a $25 RTL-SDR dongle connected to a Raspberry Pi — receives and decodes this message. Don’t make my mistake of assuming that flight tracking services are using the same data feed that ATC uses — at least if you’re analyzing what public flight trackers can and can’t show, because commercial tracking services aggregate ADS-B data from networks of volunteer and commercial receivers, and their coverage, latency, and data filtering differ significantly from the certified ATC infrastructure that air traffic controllers depend on for separation purposes.

ADS-B Out vs. ADS-B In

The FAA’s ADS-B mandate that took effect January 1, 2020 required ADS-B Out — the capability to broadcast position — for aircraft operating in Class A, B, and C airspace and above 10,000 feet MSL. ADS-B In — the capability to receive and display broadcasts from other aircraft and from ground stations transmitting FIS-B (weather) and TIS-B (traffic) data — remains voluntary. That’s what makes ADS-B In endearing to general aviation pilots flying in congested airspace — the ability to see nearby traffic on the cockpit display using ADS-B In is a genuine situational awareness improvement, particularly in VFR conditions where see-and-avoid is the primary collision avoidance methodology and the traffic display provides advance warning of converging aircraft before they’re visible to the naked eye.

The Public Tracking Ecosystem

FlightAware, FlightRadar24, ADSBExchange, and similar services aggregate ADS-B data from networks of volunteer and commercial receivers distributed globally. These services decode the raw 1090 MHz broadcasts and display them on interactive maps with historical data, flight path records, and aircraft type information matched to the Mode S transponder code. First, you should understand the difference between aggregators that honor operator privacy requests (like FlightAware and FlightRadar24, which will hide specific aircraft from public display at operator request) and ADSBExchange, which explicitly does not honor opt-out requests — at least if you’re following a specific aircraft or trying to understand why certain flights don’t appear on consumer tracking services.

Security and Privacy Limitations

ADS-B broadcasts are unencrypted and unauthenticated — any receiver can decode them, and an attacker with transmit capability could in theory inject false ADS-B messages. This security limitation is well understood by aviation security researchers, and the FAA has been evaluating ADS-B authentication mechanisms to address spoofing risks. Aircraft operators who want to limit public visibility can register with tracking services for voluntary suppression of their Mode S code from public displays, but this only affects the commercial aggregators that honor such requests — technically, anyone with a receiver can still see the raw broadcasts.

Building Your Own ADS-B Receiver

The enthusiast community around ADS-B tracking is significant. An inexpensive RTL-SDR USB dongle, a 1090 MHz antenna, and a Raspberry Pi running dump1090 or similar software is sufficient to receive and decode local ADS-B traffic. Contributing decoded data to networks like ADSBExchange or FlightAware provides these services with broader geographic coverage while giving the contributor access to premium subscription features. The technical accessibility of ADS-B reception — a $25 hardware investment and free open-source software — is what makes the ADS-B tracking community endearing to aviation hobbyists who want to engage directly with real-world air traffic data rather than consuming it through a commercial interface.