• SBAS improves GPS accuracy using both satellites and ground stations. (Geoscience Australia)
    SBAS improves GPS accuracy using both satellites and ground stations. (Geoscience Australia)

Airservices Australia yesterday announced an aviation trial of a Space-based Augmentation System (SBAS) would commence under Geoscience Australia.

SBAS is new technology that increases the accuracy of signals from global navigation satellite systems (GNSS) such as GPS. Most GNSS signals are accurate to around 5- 10 metres, but SBAS has the potential to reduce that to 10 cm.

The trial is one of more than 25 being undertaken across multiple sectors, funded through a $12 million Australian government program.

Airservices CEO Jason Harfield said the new technology would greatly benefit regional airlines and the Royal Flying Doctor Service.

“This trial will test three new technologies: first generation SBAS, second generation SBAS and what’s known as Precise Point Positioning,” he said. “It will improve safety, guiding pilots with greater accuracy, especially those flying into regional aerodromes operating under Instrument Flight Rules.

“SBAS assisted approaches are eight times safer than those which use ground-based navigation aids.

“This extraordinary new technology, which provides improved navigation and timing over GPS, will also decrease the likelihood of go-arounds and cancelations or diversions due to variable weather."

Geoscience Australia is leading the SBAS trial in Australasia in partnership with Land Information New Zealand and the global technology companies GMV, Inmarsat and Lockheed Martin.

Several SBAS systems are already in place around the world such as WAAS in the USA, EGNOS in Europe and MSAS in Japan. Most of the Southern Hemisphere, including Australia and New Zealand, has no SBAS coverage.

What does SBAS mean for GA?

SBAS technology would enable pilots to fly a three-dimensional approach called Localiser Performance with Vertical Guidance (LPV), which would enable straight-in approaches via a series of waypoints with both lateral and vertical positioning. It is thought that straight-in approaches are up to 25 times safer than a circling approach.

Current systems such as RNAV still require the altitude to be set from a barometric altimeter.

Private IFR pilots also stand to gain from SBAS, provided the aircraft has a TSO C145/C146 GNSS. TSO C129 avionics cannot use SBAS. A unit such as Garmin's GNS 430W with a current navigation database would be suitable. Depending on implementation decisions, it may be necessary for some units to have a software update so that the unit “knows” about the future Australian SBAS.

The aircraft would also need to have the GNSS interfaced to a Course Deviation Indicator (CDI) or a Horizontal Situation Indicator (HSI) with a vertical glide path indicator. Almost all aircraft that can fly via lateral navigation (LNAV) will already have this connenction. There may be some aircraft where the GNSS has been linked to a CDI with lateral guidance only.

The Australian Airline Pilots Association (AUSALPA) wrote a position paper in February this year stating that SBAS technology could have likely prevented approach accidents such as those as Benalla in 2004, Lockhart River and Mount Hotham in 2005 and Kokoda, PNG, in 2009.

 – with extra material from Andrew Andersen

comments powered by Disqus