Australian Maritime Safety Authority (AMSA) has announced they will be shutting down their DGPS Correction Beacon service. This is regarding modern GNSS services outperforming the DGPS service, ASMA made this statement on the subject ‘the increased accuracy of GPS and introduction of other global positioning constellations including GLONASS, GALILEO and Beidou, mean that AMSA’s DGPS service is no longer needed’.
Why was DGPS Discontinued
It is important to note the ASMA has stated that this discontinuation of its service is because the current accuracy of GPS exceeds that of the accuracy provided by AMSA’s Correction Beacon.
- In the year 2000, the US disabled Selective Availability (SA) from their GPS network. This improved GPS accuracy to better than 10m. One of the main reasons ASMA setup their DGPS service was that SA could have inaccuracies of up to 200m. To mitigate this some national aids to navigation authorities established marine radio beacon DGPS stations.
- Analysis of the GPS Standard Positioning Service (SPS) performance for 2018 indicated an average horizontal accuracy of better than 9m.
- The international (IMO) requirement for worldwide radio-navigation systems in ‘harbour entrances, harbour approaches and coastal waters’ is that the system should provide positional information with an error no greater than 10m (95% probability)
- In 2003, IMO’s GPS receiver performance standards introduced ‘Receiver Autonomous Integrity Monitoring (RAIM)’ technology. This technology alerted users to any inaccuracies with satellites or their signals. This in turn reduces the relevance of ASMA’s DGPS service for integrity monitoring purposes.
- The differential correction provided by ASMA’s DGPS service only applies to GPS. Modern navigation systems rely on other GNSS services to varying degrees such as GLONASS, Galileo and BeiDou as well as GPS.
- Multi-constellation GNSS receivers provide increasingly accurate positioning information
- In the next 2-3 years an Australian Satellite-Based Augmentation System project, led by Geoscience Australia will offer higher accuracy position for GNSS users.
- Majority of equipment manufacturers no longer support the hardware and firmware for DGPS reference stations
How will the discontinuation of DGPS impact you
For the majority of maritime users, this discontinuation should not impact the accuracy of satellite positioning or the safety of navigation. The only impact will be on GNSS receivers that have an integrated DGPS/DGNSS receiver. These will no longer receive ASMA’s DGPS corrections and may alert or alarm.
If have any legacy hardware that does still primarily rely on the AMSA Correction Beacon you can talk to the team at Johnny Appleseed GPS for a solution.