What is GNSS?

GNSS stands for Global Navigation Satellite System — the collective term for any satellite constellation that provides worldwide positioning, navigation, and timing (PNT) services. The four primary GNSS constellations are GPS (USA), GLONASS (Russia), Galileo (EU), and BeiDou (China), supplemented by regional systems like QZSS (Japan) and NavIC (India).

How GNSS Works

A GNSS receiver determines its position by measuring the time it takes for signals to travel from multiple satellites. Each satellite continuously broadcasts its precise location and the exact time the signal was transmitted. By measuring the signal travel time from at least four satellites and multiplying by the speed of light, a receiver can calculate its distance (pseudorange) to each satellite — a process called trilateration.

Standard GNSS positioning achieves 2–5 metre accuracy under open-sky conditions. Errors introduced by the ionosphere, troposphere, satellite clocks, and multipath reflections limit this accuracy. GNSS correction services such as RTK (Real-Time Kinematic) and PPP-RTK reduce those errors to achieve centimetre-level accuracy suitable for precision applications.

Modern receivers simultaneously track signals from multiple constellations (multi-constellation GNSS), improving availability, accuracy, and robustness — especially in challenging environments like urban canyons or dense foliage.

GNSS vs. GPS: What’s the Difference?

GPS is a specific GNSS constellation owned by the US Government and operated by the US Space Force. GNSS is the broader term encompassing all satellite navigation systems, including GPS. Using “GPS” as a generic term for satellite navigation is technically inaccurate — though widely understood colloquially.

For precision applications, leveraging all available GNSS constellations simultaneously (not just GPS) significantly improves positioning performance, fix reliability, and robustness in challenging environments.

GNSS Error Sources

Standalone GNSS accuracy is limited by several error sources:

• Ionospheric delay: charged particles in the ionosphere slow and bend satellite signals, causing positioning errors of up to 10 metres.
• Tropospheric delay: water vapour and atmospheric pressure affect signal propagation, contributing 0.5–2 m of error.
• Multipath: signals reflecting off buildings or terrain arrive at the receiver via indirect paths, corrupting measurements.
• Satellite clock and orbit errors: small inaccuracies in broadcast satellite positions and clock offsets accumulate over time.

GNSS correction services model and mitigate these errors to achieve centimetre-level positioning. Learn more: What are the Different GNSS Correction Methods?

Applications of GNSS

GNSS underpins a vast range of industries:

1. Automotive & ADAS: lane-level navigation, ADAS safety features, and autonomous driving.
2. Robotics: autonomous lawnmowers, delivery robots, and agricultural machines.
3. Drones & UAVs: precise waypoint navigation and payload delivery.
4. GIS Mapping & Surveying: centimetre-accurate data capture for infrastructure and resource management.
5. Fleet Management: real-time asset tracking and route optimisation.
6. Mobile & Handsets: lane-level navigation on consumer devices.