GPS vs GNSS: what’s the difference?

If you’ve ever used a satnav, smartphone map, or precision navigation device, you’ve probably come across the terms GPS and GNSS. They’re often used interchangeably, but they don’t mean the same thing. In fact, understanding the difference can be critical if you work in industries like surveying, automotive testing, aviation, or geospatial analysis. 

In this post, we’ll break down what GPS and GNSS really are, how they work, and why the distinction matters when it comes to accuracy, reliability, and performance. 

GPS stands for Global Positioning System. It’s a satellite navigation system developed, owned, and operated by the United States government. 

• Origins? GPS was originally built for military use in the 1970s and became fully operational in the 1990s. 

• How does it work? A network of at least 24 operational satellites orbiting Earth transmits signals to GPS receivers on the ground. By calculating the time it takes for each signal to arrive, the receiver can determine its distance from each satellite and triangulate its position. 

• Coverage? GPS provides global coverage, but all satellites in the system are operated by the US. 

GPS is one satellite navigation system, from the USA. It’s not the only one out there.

GNSS stands for Global Navigation Satellite System. This is the umbrella term for any satellite navigation system. So the difference between GPS and GNSS is that GPS is a type of GNSS system – also known as a constellation.  

Crucially, GNSS can refer to all the different constellations working together. 

Major GNSS constellations include: 

• GPS (USA) 

• GLONASS (Russia)  

• Galileo (European Union)  

• BeiDou (China)  

• QZSS (developed by Japan to enhance GPS in the Asia-Oceania regions)  

• NavIC (India, regionally)  

A GNSS receiver can use signals from multiple constellations, often simultaneously. A GPS navigation system, by contrast, can only use signals from the GPS constellation.  

GNSS is the broader category. GPS is just one member of the GNSS family.  

Both GPS and GNSS are used to provide position data for a wide range of applications. You might be tracking the position of a car on a test track when testing its autonomous emergency braking systems, or georeferencing survey data during an aerial survey. The decision about whether to use GPS or GNSS comes down to the level of accuracy and redundancy you need for your application. 

In positioning, more satellites generally mean better results. Multi-constellation GNSS receivers can see satellites from multiple constellations, which improves satellite geometry, the relative positioning of satellites in the sky. Better satellite geometry leads to reduced position dilution of precision (PDOP) and greater accuracy of position. For example, a GPS-only receiver might track 8 to 12 satellites at a given moment. A GNSS receiver using GPS, Galileo, and GLONASS could track 20+ satellites at once.  

That’s not to say that GPS-only systems perform poorly. The GPS constellation is designed to function globally and does so. But using multiple constellations can provide you with even greater precision than using GPS alone, and also provides redundancy. In GNSS-challenged environments, where buildings, trees, or terrain may block some signals, being able to see more satellites gives you a higher chance of maintaining a lock on enough satellites to calculate a precise position. 

Relying solely on GPS ties your positioning capability to the health, maintenance, and policy decisions of a single country’s system. While GPS is extremely robust, it’s still possible for outages or signal degradation to occur, whether planned (for maintenance) or due to unexpected events. GNSS mitigates that risk by tapping into multiple systems. If one constellation experiences problems, your receiver can keep working by relying on others. In the case of Automotive Testing, or Precision Agriculture, for example, GNSS can allow for improved accuracy and reliability in mixed urban/rural environments. 

Do You Always Need GNSS? Not necessarily. For casual navigation, GPS is more than enough. The extra precision and redundancy of GNSS come into play when: 

• You need centimetre-level accuracy (e.g., with RTK corrections). 

• You work in environments where satellite visibility is limited. 

• You can’t afford downtime due to signal loss. 

GNSS is of vital importance to nearly every navigation and positioning system in use on the planet. From autonomous vehicles to testing vehicle dynamics in high-performance sports cars, GNSS offers highly accurate and highly reliable position data – in most cases. 

It’s worth noting that GNSS alone, even when using multiple constellations, has limits. If the signal is lost completely (e.g., in a tunnel), accuracy will degrade quickly. And, like any system, it will suffer from some level of drift over time as small errors in the calculations used to convert the data into position accumulate. 

That’s why many high-end positioning systems, like the OXTS RT3000 v4, combine GNSS with an inertial navigation system (INS). The INS uses accelerometers and gyroscopes to track movement during GNSS outages, maintaining accuracy until the signal is restored. This fusion of technologies makes the most of GNSS’s strengths while compensating for its limitations. 

At OXTS, this approach is being pushed even further. We have built navigation systems that combine GNSS data, inertial navigation data, and data from other sensors such as LiDAR to provide centimetre-level accuracy even underground, where no satellite signal reaches. This has uses in  

To summarise, then: 

GNSS stands for Global Navigation Satellite System, and refers to any (or all) of the different GNSS constellations, including GPS.  

GPS  is America’s GNSS constellation, though it does provide global coverage.  

Using multiple GNSS constellations generally offers better accuracy, redundancy, and reliability than relying on GPS navigation alone. For critical, high-precision, or safety-related applications, GNSS, especially when combined with INS, is the superior choice.  

By understanding the difference between GPS and GNSS, you can make informed decisions about the navigation technology that best fits your needs, whether that’s a smartphone in your pocket or a high-performance automotive testing platform. 

OXTS has provided highly reliable position data to localisation and navigation projects for over twenty five years. Our mission is to help our clients to push the boundaries of what can be done with positioning technology, helping them make the world a better place one innovation at a time. From building safer vehicles to uncovering new insights about the world around us, OXTS technology ensures that you can rely on your hardware to produce accurate data, every time. 

To learn more about the role of positioning technology in different industries, click below to learn more.