Effective 1st July 2020, AMSA is shutting down its radio beacon differential global positioning system (DGPS) service. The decision came in view of a modernization of the GPS constellation.

As such, DGPS receivers will no longer receive the AMSA radiobeacon DGPS signal in areas where it was previously available. This may generate a ‘lost signal’ alarm, but the receiver will still provide a GPS derived position.

For the vast majority of maritime users, the discontinuation of AMSA’s DGPS service will not impact the accuracy of satellite positioning or safe navigation, AMSA stressed in a new marine notice.

AMSA established its radiobeacon DGPS service in the 1990’s, to improve the accuracy and integrity of global positioning system (GPS) information for ships navigating off the coast of Australia.

At the time, the publicly available GPS signal was intentionally degraded, resulting in large position errors of up to 200 metres.

Augmentation was necessary to correct for these errors and meet minimum requirements for maritime positioning and navigation.

In 2000, the intentional error in GPS positioning was removed. Since then, system technology has improved and the GPS constellation has been modernised. Observed positional accuracy for unaugmented GPS now consistently meets IMO requirements for accuracy in harbour/harbour-approach navigation.