Differential GPS licensing guide | ACMA

Differential GPS licensing guide

differential GPS jpg

Do you use or supply equipment which uses Differential GPS (DGPS) technology? This web page provides you with general information about new licensing requirements as a result of changes in the 400 MHz band.

Download our handy factsheet, Differential GPS licensing (PDF).

What is DGPS?

Differential GPS is an enhancement of the Global Positioning System (GPS). It uses a local radio signal to improve the accuracy of the position coordinates calculated by a GPS receiver.

DGPS technology achieves a high degree of technical precision. By using DGPS, a surveyor can increase the precision of the coordinates of the land being mapped to within several millimeters by adjusting readings presented by a GPS with correction data provided by a radiocommunications transmitter.

DGPS can be used in a number of ways, however this information is targeted at applications in the 400 MHz band.  

How have changes in the 400 MHz band affected DGPS?

Following a review of the 400 MHz band, we implemented a number of changes to support new technologies, reduce congestion and to provide spectrum exclusively for government use. The harmonised government spectrum (HGS) will be primarily used by state and territory governments for law enforcement, emergency services and public safety communications.

Before this review, many DGPS operated within Segment T (457.50625–459.9875 MHz) and Segment Y (467.50625–469.9875 MHz). These segments are now part of the HGS.

All non-government users operating DGPS equipment licensed to operate in a high- or medium-density area were required to transition out of the HGS by 31 December 2015. All non-government users operating DGPS equipment in low- or remote-density areas have until 31 December 2018 to relocate.

For further information on the 400 MHz band review and changes, visit the 400 MHz hub.

What are the licensing requirements for DGPS?

The information provided here about licensing requirements for DGPS equipment and its associated service is of a general nature and should not be treated as legal advice. It is recommended that DGPS operators speak with their supplier first about their specific equipment and operating requirements.

The operation of all DGPS equipment must be authorised by a relevant radiocommunications licence.

The operator can hold the licence themselves or have written permission from a current licensee under a third-party arrangement.

All of the licence conditions must be met, including:

  • the permitted operating frequency
  • bandwidth
  • allowable transmitting power
  • location
  • antenna details.

The licence issued will allow DGPS operation at one fixed site (site-specific operation) or within a larger geographic area (area-wide operation). These are the key differences:

Site-specific operation

Area-wide operation

  • operation is at a single location
  • fixed location
  • protected against interference
  • operation is short term; as a guide usually less than four weeks at any single location
  • large geographic area of operation
  • no protection from interference 
  • the service may not cause interference to coordinated services operating at specified sites

Area-wide operation

Operators of DGPS equipment will typically move from one location to another and will require an apparatus licence in which operation is permitted within a geographic area on an itinerant basis.

In accordance with the frequency assignment practice, Guideline No.2 – Area wide land mobile services used in support of differential GPS and other high duty cycle data applications, an area-wide licence authorises operation on a ‘short term’ basis at unspecified locations within the designated geographic area(s). Operations of around four weeks or less at a given location are generally considered ‘short term’.

Under the 400 MHz plan, 10 single frequency channels with 12.5 kHz bandwidth have been reserved for area-wide DGPS use (highlighted in yellow).

Band plan segment


Frequency (MHz)

12.5 kHz bandwidth

25 kHz bandwidth 

Segment S














Segment X














Due to the limited number of frequencies designated for area-wide operation, it is recommended that a minimum of two frequencies be obtained. This will provide DGPS equipment operators with an alternative frequency if interference occurs to one of the frequencies.

Area-wide operation is not given interference protection because of coordination limitations, and so it is recommended that DGPS operators review the Register of Radiocommunications Licences to determine whether site-specific operation is located in the intended area and coordinate their area-operation accordingly. 

Site-specific operation

A site-specific DGPS service is licensed to operate from a known fixed location. Under this licence, the DGPS operator is not permitted to operate at other locations.

DGPS equipment authorised for site-specific operation will be coordinated with other radiocommunications services in the area and offered interference protection.

A site specific licence is the best option for uses such as construction projects where a DGPS system will be used for a number of months or years.

Any frequencies allocated for this type of operation will not be taken from the 10 frequencies identified for area-wide operation (refer above).

Supplementary devices, such as repeaters, may be operated under this licence type. However, the supplementary device must be recorded on the licence.

What power can a DGPS service transmit?

There are four density areas in Australia that inform the authorised transmitter power, in addition to setting the apparatus licence fee for the DGPS service. These areas are:

  • high density: Sydney/Wollongong, Melbourne/Geelong and Brisbane/Gold Coast
  • medium density: Perth, Adelaide and Newcastle
  • low density: East Australia, Western Australia, Tasmania and Darwin
  • remote density areas: elsewhere.

To view these areas, see the apparatus licence fee density maps.

For area-wide operation, licensees in high and medium density areas are restricted to 8.3 watts EIRP (Effective Isotropic Radiated Power). Whereas in low and remote areas, licensees are able to operate up to 83 watts EIRP.

Licences for site-specific operation will have the maximum EIRP specified on the licence.

Always refer to the licence for information on the authorised EIRP.

What are the licensing fees?

To calculate the licensing cost of DGPS operation, see our apparatus licence fees page, and download the apparatus fee schedule.

Is your DGPS equipment authorised?

Factsheet_Is your DGPS equipment authorised

Download a printable version of the fact sheet (PDF).

Need help?

Speak to your supplier about your equipment and whether it is appropriately licensed and operating on the right transmitter power.

If you require further information about licensing requirements or the costs associated, please call the ACMA’s Customer Service Centre on 1300 850 115 or info@acma.gov.au. You can also contact an accredited person.

Last updated: 02 November 2016