ADS-B vs Radar vs MLAT: Explained Simply

There are three terms you will run into when learning how aircraft are tracked: ADS-B, radar, and MLAT. They sound technical, but the ideas behind them are simple. This guide explains ADS-B vs radar vs MLAT in plain English, so you understand how the planes get onto your screen.

The quick version

Modern consumer flight tracking relies mainly on ADS-B, sometimes topped up with MLAT. Radar is largely the domain of air traffic control.

Radar: the traditional method

Radar is the oldest of the three. There are two main types:

• Primary radar sends out a radio pulse and listens for the echo bouncing off the aircraft. It can detect aircraft even if they transmit nothing, but it gives limited information.
• Secondary radar interrogates the aircraft's transponder, which replies with information like identity and altitude.

Radar is reliable and important for air traffic control, but the equipment is expensive and the position data is generally less precise than GPS. It is not what powers most consumer tracking apps.

ADS-B: the aircraft tells you

ADS-B flips the model. Instead of the ground measuring the aircraft, the aircraft works out its own position using GPS and broadcasts it openly, several times a second.

This has big advantages:

• Accuracy: position comes straight from GPS.
• Rich data: the broadcast includes identity, altitude, speed, and more.
• Openness: the signal is not encrypted, so anyone with a receiver can use it.

This openness is exactly why free, community-based flight tracking exists. For the full explanation, read what ADS-B is and how aircraft tracking works and how flight tracking works without a subscription.

MLAT: clever geometry

MLAT, short for multilateration, is a neat trick for locating aircraft that transmit a signal but do not broadcast their GPS position, for example older transponders.

Here is the idea: the aircraft's signal reaches several ground receivers at very slightly different times, because each receiver is a different distance away. By comparing these tiny time differences across four or more receivers, the system can calculate where the aircraft must be.

MLAT requires several receivers within range and good geometry, so it works best in areas with dense receiver coverage. It is a valuable supplement to ADS-B rather than a replacement.

How they work together

In practice, a flight tracking service may:

1. Use ADS-B as the primary source, since most aircraft broadcast a GPS position.
2. Fall back to MLAT for aircraft that transmit a signal but no position.
3. Leave radar to air traffic control, which has its own infrastructure.

This layered approach maximises how many aircraft can be shown, though some, such as many military jets, still will not appear. We explain that in why you cannot see military or private jets.

What this means for you

For everyday flight tracking, the takeaway is simple: the planes you watch over your home are almost always there thanks to ADS-B, broadcasting their own accurate GPS position. That is the data a device like PlaneTicker Desktop uses to show the aircraft overhead in real time, with no subscription.

Want to see it in action? The free demo shows the ADS-B-tracked aircraft over any location you choose, right in your browser.