What Is SBAS?

What is SBAS?

SBAS is an established technology that can augment standalone Global Navigation Satellite Systems such as GPS, GLONASS, Galileo and Beidou in a number of areas including accuracy, integrity and availability. It works by collecting raw positioning data from Continuously Operating Reference Stations (CORS) in the region, computing error corrections and disseminating these corrections to users from a geostationary communications satellite via an uplink ground station. Critically for aviation purposes, the SBAS signals also provide a continuous measure of system integrity, allowing use for vertical guidance during aerodrome approaches.

Alongside the strong benefits to the Aviation sector, the SBAS technology presents significant opportunities for maritime and terrestrial use. The standard SBAS L1 service will be made available through a wide array of commercially available devices; the specification sheet of all GNSS devices will mention any SBAS compatibility. There are many L1 SBAS capable receivers already in use across Australia and New Zealand, these devices can expect to see improved positioning accuracy and precision, once configured to recognise the new SBAS Pseudo-Random-Noise identifier for the operational service (during the Test-phase, the PRN is 122).

The Australia and New Zealand Test-bed was different to established SBAS systems in a few key ways. The currently operational SBAS systems elsewhere provide only one service, which is a single-frequency L1 augmentation service to GPS. The Test-bed included three services:

  • L1 SBAS
  • Dual Frequency Multi Constellation (DFMC) SBAS
  • Precise Point Positioning (PPP)

DFMC is a second generation SBAS based on L1 and L5 frequencies and both GPS and Galileo constellations. This is a new service, the standard for which was released in February 2019, after the completion of the Test-bed. DFMC has shown potential to improve upon L1 SBAS to further improve, precision, and integrity in a range of use cases and environments.

PPP is a different kind of service that allows for accuracies around the decimetre level, with the additional requirement of a 30-40 minute convergence time.

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