Sub-Commission 4.2

Multi-frequency Multi-constellation GNSS

Chair: Suelynn Choy (Australia)
Vice Chair: Sunil Bisnath (Canada)

Terms of Reference

The year 2020 marks a new era of multi-constellation GNSS with increased number of available satellites in different orbits, diverse signals/frequencies, and new correction products and services. This ongoing modernization offers exciting prospects for further improvement of high precision GNSS PNT and open up new areas of research and innovation. For example, the increased number of satellites and signals-in-space improves the performance of precise positioning applications; the available of addition frequency signals (beyond L1 and L2) enables new concepts for signal quality assessment and improved carrier phase ambiguity resolution techniques; multi-GNSS satellite metadata to allow determination of GNSS-based terrestrial reference frame scale, orbit determination; as well as new services such as Precise Point Positioning (PPP) and emergency warning services.
Recognizing the central role of GNSS in enabling high precision PNT, SC4.2 will foster research to address interoperability of high precision GNSS, which includes standards, theory, algorithms development and applications of multi-GNSS. In addition, SC4.2 will encourage research in emerging areas such as carrier phase positioning and ambiguity resolution for mass-market GNSS positioning; as well as GNSS PNT and LEO constellation.
SC4.2 will coordinate activities to promote and deliver practical and theoretical solutions for engineering and scientific applications and also will stimulate strong collaboration with the IAG Services (IGS) and relevant scientific and professional sister organizations such as FIG, ION and IEEE.


The objectives of SC4.2 are:

• Identify and investigate important scientific and technical issues in multi-frequency multi-constellation GNSS
• Encourage international collaboration in new areas of research and innovation
• Promote interoperability and compatibility of GNSS
• Promote development of GNSS applications in the Asia Pacific region and contribute to capacity building of GNSS education and training
• Encourage partnerships across research, government and industry on applications of multi-frequency multi-constellation GNSS

WG 4.2.1: Interoperability of GNSS precise positioning (Joint WG between IAG and IGS)

Chair: IAG Rep to ICG.TBC
Vice-Chair: Sharyl Byram (USA)

The objective of this WG is to promote interoperability of GNSS precise positioning to support a wide range of science and engineering applications which will benefit society. Activities include: (1) encourage sharing and dissemination of knowledge of satellite parameters and receiver properties which are essential for high precision GNSS applications; and (2) investigate new techniques and algorithms to ensure interoperability of correction products for precise point positioning (PPP).
This WG will work in close scientific collaboration with IGS, FIG and ICG.

WG 4.2.2: Ambiguity resolution for low-cost GNSS positioning

Chair: Prof. Xiaohong Zhang (China)
Vice-Chair: Dr Robert Odolinski (New Zealand)

In the past few decades the American GPS and Russian GLONASS have been the dominant satellite systems in Geodesy and Geophysics applications. Recent developments in Global Navigation Satellite Systems (GNSSs) involve the Chinese BeiDou Navigation Satellite System (BDS), Japanese Quasi-Zenith Satellite System (QZSS), European Galileo, and modernization of triple-frequency GPS and GLONASS signals. Through the many more line of sights and frequencies obtained in a combined multi-GNSS model, one can improve the positioning reliability and accuracy when compared to using any of the satellite systems separately. The challenges lie however in formulating rigorous models and algorithms to link these satellite observations to the parameters of interests.
Low-cost multi-GNSS receiver development has taken a revolutionary role in precise positioning applications in the past few years. By combining several GNSSs, it has been demonstrated that a competitive low-cost positioning performance can be obtained to that of using survey-grade GNSS receivers and antennas. Smartphone manufacturers have started to take advantage of such low-cost GNSS chips, which has led to precise positioning applications in smartphones as well. The research conducted will focus on algorithms and methods for integer ambiguity resolution on low-cost handheld devices, to facilitate optimal modelling of precise positions and atmospheric delays (ionosphere and troposphere), to investigate the quality control methods for low-cost GNSS precise positioning, to develop a robust algorithms of integration GNSS with MEMS and other low-cost sensors.

WG 4.2.3: GNSS and LEO constellation

Chair: Prof. Xingxing Li (Germany)
Vice-Chair: Dr. Safoora Zaminpardaz (Australia)


There has been significant development in building large LEO constellations of satellites to provide a positioning, navigation and timing service. These LEO constellations give us a great opportunity to create new LEO-augmented GNSS technologies and applications, and even to open up new research areas. However there are many challenges. This WG is devoted to promote research, develop models and algorithms, and study theoretical and practical foundations for LEO-augmented GNSS technologies. The main research focus will include, but not limited to, LEO-augmented GNSS precise positioning with rapid convergence, integrated precise orbit determination, LEO-GNSS meteorology and ionospheric sounding methodology, terrestrial reference frame realization, etc. Many efforts will also be made to stimulate strong collaborations among researchers and international organizations.

WG 4.2.4: Multi-GNSS in Asia

Chair: Prof. Chalermchon Satirapod (Thailand)
Vice-Chair: Prof. Hung-Kyu Lee (Korea)

As the Asia Oceania GNSS downstream market continues to grow rapidly, the role of the WG is to further promote GNSS scientific research, development and applications in the region. It will also focus on education and capacity building such as training, research, and networking activities to encourage the next generation of GNSS researchers. The working group will work in close cooperation with Multi-GNSS Asia (MGA) to promote applications of GNSS and SBAS such as in surveying, construction, agriculture, transportation and logistics, as well as emergency response and disaster management.