Real-Time Precise Point Positioning Utilising the Japanese Quasi-Zenith Satellite System (QZSS) LEX Corrections Suelynn Choy1, Ken Harima1, Shaocheng Zhang1, Yong Li2, Yaka Wakabayashi3, Hiroaki Teteshita3, Satoshi Kogure3, and Chris Rizos2 1School of Mathematical and Geospatial Sciences, RMIT University, Australia 2School of Civil and Environmental Engineering, University of New South Wales, Australia 3Satellite Navigation Office, Space Applications Mission Directorate I, Japan Aerospace Exploration Agency, Japan

Outline Overview of the Japanese Quasi-Zenith Satellite System (QZSS) Introduction to the QZSS LEX signal CRCSI-JAXA Project Utilisation of LEX signal for Precise Point Positioning (PPP) Post-processed LEX-PPP experiment Real-time LEX-PPP experiment Future work Note: LEX – L-band EXperimental CRCSI – Cooperative Research Centre for Spatial Information JAXA – Japan Aerospace Exploration Agency RMIT University PPP Workshop 2013, Ottawa

Introduction to QZSS RMIT University PPP Workshop 2013, Ottawa

Quasi-Zenith Satellite System (QZSS) The Quasi-Zenith Satellite System (QZSS) developed by Japan Aerospace Exploration Agency (JAXA) is a regional navigation satellite system, which uses a constellation of satellites placed in highly-inclined elliptical orbits. This is to ensure that one of the satellites is always visible near zenith over Japan, including in urban and mountainous areas whereby it is difficult to receive GNSS signals. MICHIBIKI means “Guiding” or “Showing the way” Multiple satellites on the quasi-zenith orbits ©JAXA Asymmetry orbit in the shape of a ‘figure 8’ ©JAXA RMIT University PPP Workshop 2013, Ottawa

Overview of QZSS Functional Capability: Coverage: Signals: GNSS complementary Improve availability Improve accuracy Coverage: East Asia and Oceania Signals: L1C/A, L1C, L2C and L5 positioning L1-SAIF on 1575.42 MHz LEX on 1278.75MHz First QZSS Satellite ‘Michibiki’: Launched in September 2010 Future QZSS Satellites: 2 HEO and 1 GEO End of March 2018 The first QZSS satellite ‘Michibiki’ ©JAXA augmentation – First phase JAXA-LEX PPP accuracy < 30 cm (H-RMS) - Note: SAIF – Submetre-class Augmentation with Integrity Function QZSS improves positioning accuracy ©JAXA RMIT University PPP Workshop 2013, Ottawa

Coverage Area (1 QZSS Satellite) Percentage of Time during which a Single QZS can be seen at an Elevation Angle of 10° or more (JAXA, 2012) RMIT University PPP Workshop 2013, Ottawa

Coverage Area (3 QZSS Satellites) Percentage of Time during which at least One QZS in the 3-satellite QZSS constellation can be seen at an Elevation Angle of 10° or more (JAXA, 2012) RMIT University PPP Workshop 2013, Ottawa

Introduction to LEX Signal RMIT University PPP Workshop 2013, Ottawa

QZSS LEX Signal QZSS Signals: LEX (L-band EXperimental) Signal: GPS compatible signal for positioning : L1C/A, L1C, L2C and L5 GPS augmentation: L1-SAIF and LEX LEX (L-band EXperimental) Signal: For experimental purposes Frequency: 1278.75 MHz (similar to Galileo E6) Message rate: 2 Kbps For high accuracy (cm-level) positioning applications experiment, e.g. Precise Point Positioning (PPP) LEX (L-band experiment) is a unique signal from "MICHIBIKI". The objectives of LEX signal are to enhance the performance of GPS(realizing improved precision) and to establish the next generation's positioning based technology. Note: SAIF – Submetre-class Augmentation with Integrity Function RMIT University PPP Workshop 2013, Ottawa

QZSS LEX Signal Specifications Item Specification Frequency 1278.75MHz (Galileo E6) Bandwidth 42.0MHz Signal Power -155.7dBW (Min) Modulation Kasami-sequences, BPSK(5), short-code/long-code Spreading Code Short Period: 4ms, Length: 10,230 chips Long Period: 410ms, Length: 1,048,575 chips Navigation Data Short-code: 2000 bits/frame, 1 frame/s Long-code: data-less RMIT University PPP Workshop 2013, Ottawa

LEX Message Structure RMIT University PPP Workshop 2013, Ottawa

Message Type Definition Content Notes 0-9 Spare (System use) 10-19 10 Signal health (35 satellites) Ephemeris & SV clock (3 satellites) For JAXA experiment 11 Ephemeris & SV clock (2 satellites) Ionospheric correction 12~19 Spare 20 For experiment by GSI 21~155 For experiment For experimental users except JAXA and GSI and users of application demonstration in private sector 156-255 For application demonstration in private sector For experimental users of application demonstration in private sector by means of performance enhancement signal Note: JAXA – Japan Aerospace Exploration Agency GSI – Geographical Survey Institute of Japan RMIT University PPP Workshop 2013, Ottawa

JAXA-LEX Message Interval (Nominal) Message Data Broadcast Update Effective Period Signal health 1 second - Ephemeris 12 seconds 3 minutes 6 minutes SV clock Ionospheric correction 30 minutes RMIT University PPP Workshop 2013, Ottawa

Joint CRCSI-JAXA LEX Project Note: CRCSI – Cooperative Research Centre for Spatial Information JAXA – Japan Aerospace Exploration Agency RMIT University PPP Workshop 2013, Ottawa

Australian Government Positioning Policy In 2012, the Australian Government developed a National Satellite Utilisation Policy (Australia’s first ever space policy) National Earth Observation from Space Strategic Infrastructure Plan National Positioning Infrastructure (NPI) Plan In April 2013, the policy was launched and released providing certainty and strategic direction for Australian users of satellite technology Australian NPI Vision Instantaneous, reliable and fit-for-purpose positioning and timing services anywhere, anytime across the Australian landscape and its maritime jurisdictions RMIT University PPP Workshop 2013, Ottawa

Australian GNSS CORS Infrastructure (Hausler, 2013) RMIT University PPP Workshop 2013, Ottawa

Motivation: CRCSI – JAXA LEX Project Aim: Evaluate the feasibility of using the QZSS LEX signal to provide a high accuracy real-time positioning service to GNSS users in Australia in support of the Australian National Positioning Infrastructure (NPI) plan Uniqueness: Opportunity to experiment with QZSS LEX signal Better acquisition and coverage of the augmentation information nationwide high accuracy positioning Robust and effective data transmission capacity e.g. lower bandwidth than the current NRTK Reduced reliance on local CORS infrastructure not constrained by baseline length and CORS coverage An alternative data communication infrastructure not restricted by land-based communication technologies e.g. 3G mobile coverage RMIT University PPP Workshop 2013, Ottawa

Evaluation of LEX Messages RMIT University PPP Workshop 2013, Ottawa

Quality of JAXA-LEX GPS Orbits and Clocks (Regional) One week: 1 to 7 January 2013 Site: Alice Spring (IGS – ALIC) RMIT University PPP Workshop 2013, Ottawa

Distribution of Test Sites in Australia 23 Australian GNSS Stations; 1 January 2013; 30s Longitude 23 Australian Continuously Operating Reference Stations (CORS) on 1 January 2013 were post-processed and analysed. RMIT University PPP Workshop 2013, Ottawa

JAXA-LEX PPP Position Errors (Post-processed) Position Error (m) The PPP accuracy in the horizontal and up directions is about ~0.3 m and ~0.6 m, respectively. The 3D precision of the estimated LEX-PPP solutions are sub-metre level. RMIT University PPP Workshop 2013, Ottawa

Real-time LEX PPP Experiment First LEX field experiment in Australia RMIT, Melbourne 8 – 10 March 2013 LEX Message Type 10 and 11 GPS-only Series of static and kinematic PPP tests RMIT University PPP Workshop 2013, Ottawa

Availability of LEX Message RMIT University PPP Workshop 2013, Ottawa

Quality of the JAXA-LEX Orbits and Clocks (Bundoora) RMS X/Y/Z/CLK: 37.4, 33.3, 35.0 cm / 2.3 ns RMIT University PPP Workshop 2013, Ottawa

Kinematic LEX-PPP Real-Time JAVAD Delta, 08/03/2013 – 09/03/2013, 1 Hz, LEX MT 10 and 11 East North Statistical computation, ignoring the first hour, using data collected from the experiment. Plot only shows daily 24 hour time series. Up RMS E/N/U: 44.1, 35.1, 71.7 cm RMIT University PPP Workshop 2013, Ottawa

Static LEX-PPP Real-Time JAVAD Delta, 09/03/2013 –10/03/2013, 1 Hz, LEX MT 10 and 11 East North Statistical computation, ignoring the first hour, but using data collected from the experiment. Plot only shows daily 24 hour time series. STD E/N/U: 16.7, 4.8, 5.1 cm Up RMS E/N/U: 23.9, 7.4, 11.1 cm RMIT University PPP Workshop 2013, Ottawa

Static IGS-PPP Real-Time JAVAD Delta, 09/03/2013 – 10/03/2013, 1 Hz, products.igs-ip.net:2101(mountpoint:CLK11) East North Ignoring the first one hour of solutions. CLK11: APC; GPS GLO; 1059,1060,1065,1066; CODE Ultra Rapid; ITRF2008; BKG RTNet + BNC Up RMS E/N/U: 3.5, 2.4, 5.4 cm RMIT University PPP Workshop 2013, Ottawa

On-going Work Evaluation of the “new” Message Type 12 Since April 2013, JAXA has started to transmit MADOCA products RTCM SSR format Evaluation of the IGS real-time service products and the Australian regional products Development of an “Australian LEX” Correction messages and “packaging” Processing algorithm and software LEX receivers Note: MADOCA – Multi-GNSS Advanced Demonstration tool for Orbit-and-Clock Analysis RMIT University PPP Workshop 2013, Ottawa

Thank you! Acknowledgements RMIT University, Australia University of New South Wales, Australia Department of Sustainability and Environment, Victoria, Australia Land and Property Information, New South Wales, Australia Geoscience Australia, Australia Japan Aerospace Exploration Agency, Japan Cooperative Research Centre for Spatial Information, Australia Thank you! RMIT University PPP Workshop 2013, Ottawa