The GDL90 Protocol

The original GDL90

The original GDL90

This device is the original GDL90 - it retails for somewhere in the region of US$8,000.
GDL90 combines GPS satellite navigation with datalink communications to deliver interactive traffic and hazard surveillance.
It has become a very popular data protocol, used with many products (particularly GARMIN), including the ForeFlight app.

Report and Receive Surveillance Data

GDL 90 is designed to transmit, receive and decode Automatic Dependent Surveillance-Broadcast (ADS-B) messages via onboard datalink.
It broadcasts your aircraft's position, velocity, projected track, altitude and flight identification to other equipped aircraft in your vicinity, as well as to ground-based transceivers maintained by the FAA.

Get Ready for Free Flight

ADS-B is a key enabling technology for Free Flight — an airspace management concept that will ultimately make flying safer and provide more efficient use of our airspace. With ADS-B you "see" aircraft traffic with much more precision than with existing ground-based radar systems. The GDL 90 is designed for development of the FAA’s Safe Flight 21 program, which is currently implementing the ground-based portion of the ADS-B network.

Enhance Situational Awareness

Benefits of the GDL 90 include tactical surveillance data for traffic and hazard avoidance. This includes the ability to receive continuous detailed weather information, as well as Temporary Flight Restriction (TFR) data and TIS-B traffic/conflict information (uplinked from ground radar). Being able to see and react to the same traffic picture that controllers are watching on their radar scopes provides an extra margin of safety in the air. And because the government plans to offer this data free of charge, the added safety comes at a real savings over similar commercial uplink services.

NOTE: GDL 90 does not meet the requirements for ADS-B compliance in 2020.


GDL90 protocol specifications 

GDL90 UAT Installation Manual