Why multi-frequency and multi-constellation matters for GPS/GNSS receivers?

GPS-GNSS-satellite-in-Orbit-Septentrio.

Multi-constellation multi-frequency GNSS receivers are used across many industries today for reliable positioning down to the centimeter level. Among various professional-grade GNSS receivers available today, there is variability in the amount of satellite constellations and signals that a receiver can access. Those receivers that have access to the highest number of constellations and signals offer the best positioning availability, accuracy and resilience even in challenging environments. They also provide access to new and upcoming services that will be made available to users via GNSS signals. These include anti-spoofing services like Galileo OSNMA and GPS Chimera, high accuracy services like Galileo HAS, QZSS CLAS, BeiDou HAS and more.  

Multi-constellation technology 

Global Navigation Satellite Systems (GNSS) is a system of satellites which broadcast signals from space with positioning and timing information. These signals are picked up by receivers which then use this information to determine their geographic location in terms of longitude, latitude and height.

GNSS vs GPS

So what is the difference between a GPS and a GNSS receiver? A simple GPS receiver only makes use of one global navigation satellite system, while multi-constellation GNSS receivers get information from many such systems at the same time. This allows them to "see" much more satellites at any given time. Septentrio GNSS receivers can connect to any satellite in each GNSS system for maximum positioning availability and accuracy.

 

GNSS Satellites Coverage
GPS            32 Global
Galileo   26+ Global
BeiDou      Phase 2: 15+
Phase 3: 25+
Global
Phase 2 mostly China regional
GLONASS  24 Global
QZSS         4+ Over Japan and Asia Pacific
NavIC        7+ Over India

 

Table 1: GNSS constellations, approximate number of satellites and coverage.  

Multi-frequency technology

Each one of the GNSS satellites uses one or more frequencies to transmit ranging signals and navigation data. These signals vary in terms of their dependability and availability. The more signals the receiver can access, the more information it can collect from the satellites, the more accurate and reliable the computed position will be.   

Navigation GPS in phones, cars and other consumer devices usually uses GPS or GNSS signals on just one frequency (L1). Dual-frequency receivers can receive two signals from each satellite system. Multi-frequency receivers, on the other hand, receive a multitude of signals from any GNSS system. Such multi-frequency receivers push the limits of GNSS technology to achieve the most accurate, reliable, and robust positioning possible.  

 

Upcoming GNSS services 

Various GNSS systems are exploring ways to add value to their satellite constellations with high-security and high-accuracy positioning services, which will be available directly via the GNSS signals in the near future. Using future-proof multi-frequency GNSS receivers allows users to take advantage of these upcoming services as soon as they become available.  

All of these services, except possibly CAS, will be offered free of charge.  

Service  Added value  GNSS  Signal  Region  Status 
OSNMA  Anti-spoofing Galileo  E1b  Global  Operational Beta

Chimera 

Anti-spoofing  

GPS  

L1C 

Global 

Not yet operational 

CAS 

Anti-spoofing (commercial)  

Galileo 

E6 

Global 

Not yet operational 

HAS 

High accuracy (decimeter ~20cm) 

Galileo  

E6 

Global 

Nearing Beta 

CLAS 

High accuracy (sub-decimeter) 

QZSS 

L6 

Japan 

Operational 

SLAS 

High accuracy (sub-meter) 

QZSS  

L1S 

Japan 

Not yet operational 

PPP-B2b 

High accuracy (decimeter ~20cm) 

BeiDou 

B2b 

China 

Operational Beta 

Table 3: Future-proof multi-frequency receivers enable users to take advantage of upcoming GNSS services