FOREWORD
Automatic dependent surveillance — broadcast (ADS-B) and multilateration (MLAT) are additional forms of electronic
surveillance that may be used to support air traffic services (ATS) in en-route and terminal area operations. While radar
was previously the only form of electronic surveillance used for these operations, ADS-B and MLAT may be introduced
in areas that are either not served, or are partially served, by radar. In view of their attractive costs, it is expected that
ADS-B and MLAT will increasingly be used in areas where radar may not be economically viable, particularly in less
demanding air traffic management (ATM) environments.
This circular provides details of a comparative assessment undertaken by the Separation and Airspace Safety Panel
(SASP) that concludes that ADS-B and MLAT can be used to provide ATS surveillance, including separation, subject to
certain conditions. The SASP assessment concluded that ADS-B can be used to provide a five nautical mile (5 NM)
minimum, subject to certain conditions being satisfied.
For guidance to States, an implementation roadmap and answers to frequently asked questions are included in
Chapter 4.
Monitoring of the deployment of State or regional implementations of ADS-B and MLAT by ICAO is anticipated.
Comments from States on this circular, particularly with respect to its application and usefulness, would be appreciated.
These comments will be taken into account in the preparation of subsequent material and should be addressed to:
The Secretary General
International Civil Aviation Organization
999 University Street
Montréal, Quebec, Canada H3C 5H7
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