GNSS Applications:
What is GNSS?
Global Navigation Satellite Systems (GNSS) are networks of satellites in space that send position and timing data to GNSS receivers for geolocation purposes. Once received, the GNSS receiver uses the data to determine precise earth-based locations and track movements over a journey.
GNSS provides near-global coverage and is used in a wide array of applications. Some of the most vital are military operations, maritime shipping, air travel, mapping, and smartphone services.
GNSS vs. GPS
GNSS, as described above, are global networks of satellites that provide location and timing data for numerous earth, atmospheric, and space-based applications.
GNSS is a broad term encompassing different types of satellite-based positioning services. GNSS satellites in Low Earth Orbit (LEO) transmit signals to a GNSS or GPS receiver, which then use trilateration to determine their location on the surface of the Earth. Simply put, GNSS receivers determine their location by measuring the time it takes a signal to travel from the GNSS receiver to four or more nearby satellites.
While GNSS is a broad and encompassing term, GPS (Global Positioning System) is a single satellite positioning service operated by the United States of America.
The primary difference between GPS and GNSS technology is that a GNSS receiver is compatible with GPS, but not all GPS receivers are compatible with GNSS. Since there are more operational GNSS satellites than GPS-specific satellites, GNSS systems often provide more accuracy and reliability, but only in some applications.
GPS was developed by the US Department of Defense in the 1970s and was built primarily for US military applications. Today, however, GPS has evolved to encompass applications that involve nearly everything we do in our daily lives.
Examples of GNSS Systems
The most widely used GNSS system in the world is the Global Positioning System (GPS), which is owned and operated by the United States of America.
Still, other countries have satellite constellations in Low Earth Orbit (LEO), and more are beginning to plan their own launches.
Some of the most common and well-known GNSS systems are Galileo (Europe), GLONASS (Russia), BeiDou Navigation Satellite System (China), QZSS (Japan), and IRNSS/NavIC (India).
Understanding Global Navigation Satellite Systems (GNSS)
3 Segments of Global Navigation Satellite Systems (GNSS)
1. Space (Constellations)
2. Control (Master Control Stations)
3. Users (GNSS Users)
All three segments listed above are encompassed by each primary type of GNSS system.
4 Key Criteria for GNSS Performance
There are four key criteria used to validate GNSS performance.
1. Accuracy
The difference between the measured and real position of a target receiver (speed or time).
2. Integrity
The system's ability to provide a threshold of confidence.
3. Continuity
The system's ability to operate or function without interruption.
4. Availability
The percentage of time that a signal fulfills the above criteria (accuracy, integrity, and continuity).
GNSS performance can be improved by using regional satellite-based augmentation systems (SBAS). One example of SBAS is the European Navigation Overlay Service (EGNOS), which improves reliability and accuracy through signal measurement error corrections and by validating signal integrity with supplemental information.
* Improving and optimizing the above four criteria is one of the best defenses against threats like GNSS jamming, GNSS spoofing, and other types of GNSS interference.
