Field Guide · protocol

Also known as: TIS-B, Traffic Information Service-Broadcast

TIS-B (Traffic Information Service–Broadcast) is a ground-based service that uplinks a synthesized traffic picture to aircraft, so that an ADS-B In receiver can see targets that are not broadcasting ADS-B themselves.1 Ground stations fuse secondary-radar, multilateration, and ADS-B tracks and rebroadcast them on both the UAT 978 MHz and 1090 MHz links, closing the gap during the transition to universal ADS-B equippage.

radar / MLAT ground station non-equipped track TIS-B uplink ADS-B In aircraft 978 MHz + 1090 MHz
TIS-B: a ground station rebroadcasts radar/ADS-B tracks so an ADS-B In aircraft sees traffic that is not itself ADS-B equipped.

Overview

The value of ADS-B In depends on other aircraft broadcasting ADS-B Out. During the long equippage transition, and permanently for aircraft that never equip, many targets are invisible to a purely airborne picture. TIS-B fills that hole: FAA ground stations watch their surveillance sources, and for each aircraft that is receiving ADS-B, they uplink the positions of nearby traffic the aircraft would otherwise miss.

Technical characteristics

Property Value
Direction Ground-to-air (uplink)
Frequencies 978 MHz (UAT) and 1090 MHz
Source data SSR, MLAT, ADS-B fusion
Client-tailored Uplink keyed to a client aircraft’s position
Related service ADS-R (rebroadcasts across the two links)
Standard RTCA MOPS (DO-260/DO-282 families)

TIS-B is client-based: the ground station only advertises traffic within a service volume around an aircraft it knows is listening, which conserves link bandwidth. A closely related function, ADS-R (ADS-B Rebroadcast), forwards genuine ADS-B reports between the 978 and 1090 MHz links so a UAT-only aircraft and a 1090ES-only aircraft can still see each other.

History

TIS-B grew out of the earlier addressed Traffic Information Service (TIS) delivered over Mode S, reworked as a broadcast service for the ADS-B era and standardised by RTCA alongside ADS-B. It is a core element of the FAA’s NextGen surveillance architecture.

Deployment

TIS-B is operational across the U.S. ground-station network and is a primary reason general-aviation pilots value ADS-B In: combined with FIS-B weather on the same UAT link, it delivers a near-complete traffic-and-weather picture at no subscription cost. Note that TIS-B tracks can lag or drop targets in radar-only coverage, so it supplements rather than replaces see-and-avoid.

Decoding it with GopherTrunk

Not decoded. TIS-B is carried inside the UAT and 1090ES data streams as ground-originated traffic reports. GopherTrunk decodes 1090 MHz airborne ADS-B squitters but does not parse the ground-uplink TIS-B service, which on 978 MHz rides the UAT link GopherTrunk does not tune. It is receivable with a wideband SDR and dedicated UAT tooling, but sits outside GopherTrunk’s land-mobile and airborne-ADS-B focus.

Sources

  1. Traffic information service – broadcast — Wikipedia, for the TIS-B ground-uplink service, its radar/ADS-B source fusion, client-based traffic advertisement, and delivery on the 978 and 1090 MHz links. ↩

See also