Positioning using the Japanese QZSS (1.11)

The Quasi-Zenith Satellite System (QZSS) is a Japanese regional satellite navigation system that, in addition to conventional GNSS signals, transmits an augmentation signal called LEX (L‐band Experimental Signal).

This project will investigate the use of the QZSS LEX signal for delivering high accuracy real-time positioning (especially RTK-PPP) on a national basis in support of a future national positioning infrastructure (NPI).

The LEX signal is potentially suited to meeting the communications needs of the NPI. This research will demonstrate the viability of and technical considerations for using the LEX signal in this role.

This proposal takes advantage of a unique opportunity afforded the CRCSI to collaborate with JAXA on the use of QZSS in Australia. JAXA is offering dedicated access to a LEX decoder for the purposes of this project as well as access to the QZSS ground segment in order to upload test messages to the QZSS satellite for transmission via the LEX signal.


The first real-time field experiment of the MADOCA-LEX PPP was conducted in Sydney, Australia.

A pilot system to broadcast ‘Australian LEX’ corrections for PPP using the QZS-1 satellite has been implemented and tested, this included;

  • Establishing the message format for standard PPP;
  • Testing the TCP server to transmit ‘Australian LEX’ messages;
  • Modifying the RTKLIB library to process ‘Australian LEX’ messages;
  • Testing real-time PPP using ‘Australian LEX’.



The research will inform the development of the National Positioning Infrastructure Plan; expose CRCSI researchers to leading JAXA scientists and engineers; and enable CRCSI access to the space segment of a satellite positioning system for research

Project Participants

RMIT   -   UNSW   -  JAXA   -   DSE   -   LPI   -   GA