# Can ATC provide vectors and separation service to and between IFR aircraft in areas where radar coverage does not exist using ADS-B only?

In the U.S., can ATC provide vectors and separation service to and between IFR aircraft in areas where radar coverage does not exist using ADS-B only?

If so, are the separation standards the same as if the IFR aircraft were being provided radar vectors and separation service in an area where radar coverage does exist?

Yes. In the United States, ADS-B may be used as the sole surveillance source for the provision of ATC services (including IFR-IFR separation) provided that the automation system ("radar scope") is designed to use it. There are no differences between ADS-B sole-source separation standards and SSR separation standards.

a. Surveillance sources that are approved for ATC use are Primary Radar, Secondary Radar, ADS-B and WAM. Approved ATC Surveillance Sources may be used for:

a. Secondary radar may be used as the sole display source as follows:

1. In Class A airspace.
2. Outside Class A airspace, or where mix of Class A airspace/non-Class A airspace exists, only when:
(b) The primary radar is temporarily unusable or out of service. Advise pilots when these conditions exist, or
(c) A secondary radar system is the only source of radar data for the area of service. TERMINAL. Advise pilots when these conditions exist.

b. TERMINAL. Do not use secondary radar only to conduct surveillance (ASR) final approaches unless an emergency exists and the pilot concurs.
c. All procedures and requirements relating to ATC services using secondary radar targets apply to ATC services provided to targets derived from ADS-B and WAM.

b. TERMINAL.
4. ADS-B may be integrated as an additional surveillance source when operating in FUSION mode. The display of ADS-B targets is permitted and does not require radar reinforcement.
5. The use of ADS-B only information may be used to support all radar requirements associated with any published instrument procedure that is annotated “Radar Required”.

d. ERAM.
3. Up to and including FL 230 where all the following conditions are met – 3 miles:
(b) The preferred sensor and/or ADS-B is providing reliable targets.

• When using lateral separation standards ssr beacon only slashes are measured beacon end from beacon end, 3 or 5 miles, depending on distance from the antenna (i.e., what antenna) . How do you determine distance from "antenna" using ADS B? Also, do the slashes displayed with ADS-B only look the same as with standard ssr beacon slashes so you can determine the distance between two aircraft? – Apr 24 at 4:43
• In STARS the only sensor which uses ADS-B is the Fusion sensor which shows dots, not slashes; separation is based off the centers of the dots (.65 5–5–2d). Antenna distance is determined by distance to the ADS-B antenna, if that is even directly relevant for the controller, which it isn't for Terminal—the computer tells us if we need 3 or 5 miles (5–5–4b1, b2). ADS-B is an approved source (5–5–4b4, b5). I'm not experienced with ERAM but I believe the ADS-B slash is the same as the SSR slash; again, ADS-B is an acceptable source (5–5–4d3(b) and the Note below). Apr 24 at 10:16
• Interesting stuff. Don't recall ever hearing a controller "advise pilots" that only SSR is in use, and I don't really know what I'd make of the info, or do any differently, if I did. Apr 25 at 12:52
• Also, what is WAM in the above context? Apr 25 at 12:52
• @RalphJ WIDE AREA MULTILATERATION (WAM)- A distributed surveillance technology which may utilize any combination of signals from Air Traffic Control Radar Beacon System (ATCRBS) (Modes A and C) and Mode S transponders, and ADS-B transmissions. Multiple geographically dispersed ground sensors measure the time-of-arrival of the transponder messages. Aircraft position is determined by joint processing of the time-difference-of-arrival (TDOA) measurements computed between a reference and the ground stations' measured time-of-arrival. --- this is what ADS-B tracking sites call MLAT Apr 26 at 12:35

I am not 100% certain about the USA rules but in Australia which is based on ICAOs rules ADS-B is the same as SSR (Secondary Surveilance Radar) for the purpose of providing surveillance seperation. Additionally, the standards is the same standards used.

The only extra condition for ADS-B is they must be a Class 1 symbol and can not be used during forecast RAIM outage. (Australian MATS 10.2.1.4 and Australian MATS 10.2.1.4.1)

In Australia the majority of the country is covered by ADS-B but only the east coast and areas around Perth have SSR coverage. However a full surveillance service is applied where ever there is either or both SSR covereage and ADS-B coverage.

I doubt that there would be any difference in the USA.

Do not get this confused with ADS-C which is not the same as ADS-B and has different seperation standards and protocols.