Australia's differential global positioning system
The differential global positioning system (DGPS) keeps ships on course. We manage a network of 16 stations around selected areas of Australia's coast.
Our network of 16 DGPS stations are located in selected areas of Australia's coastline including:
- the Great Barrier Reef
- Torres Strait region
- Bass Strait
- the south-eastern ports
- selected port regions such as:
- Sydney (including Newcastle)
- Port Kembla
The DGPS service operates in the MF radio beacon band (285-325 kilohertz) and complies with the relevant prevailing standards of:
- RTCM (Radio Technical Commission for Maritime Services)
- IALA (International Association of Marine Aids to Navigation and Lighthouse Authorities)
- ITU (International Telecommunication Union).
This ensures that shipboard equipment on international ships are capable of receiving and using the signals.
Our Information Sheet provides further details on our DGPS stations, including the location and WGS84 coordinates of stations, a sites positional accuracy, transmission frequencies and RTCM message used.
The DGPS accurately keeps ships on course.
What is DGPS?
DGPS is a means of improving the accuracy of GPS and of providing integrity monitoring to users. DGPS involves reference stations, at precisely known locations, which provide real-time corrections and integrity information for GPS signals.
The receivers in these reference stations can estimate errors in the GPS because they have an accurate knowledge of their own position. As a result, the horizontal accuracy of the system can be improved from 100 metres (95 per cent of the time) to better than 10 metres.
DGPS uses pseudo-range corrections and range-rate corrections from a single reference station. The pseudo-ranges are simultaneously measured to all GPS satellites in view, and using the known position of the receiver's antenna, errors are calculated and provided as a differential correction.
If your vessel has a DGPS enabled transceiver, you should automatically receive our DGPS service.
How DGPS works
Effect of user-to-reference station separation on navigational accuracy
As the distance between the user and the DGPS station increases, the signal from the satellite is forced to take different paths to each location. Due to atmospheric variations, the user’s receiver experiences a different delay compared to the reference station. The greater the separation, the more difficult it becomes to correct errors.
As a result, the further the user is from the reference station, the more inaccurate the navigational data can become.