GNSS - The Global Navigation Satellite System provides accurate positional fixing services that is available to everyone around the world by combining forces. Sailors like those racing on the Vendee Globe, rely on such services.

The GNSS is an essential element for the control and monitoring of any autonomous vessel. Typically, such a system in linked to navigation hard and software, such as the proposed Captain Nemo and Hal, onboard the Elizabeth Swann. Even more important when in confined waters, such as navigating ports, harbors and marinas.

GNSS stands for Global Navigation Satellite System, and is the standard generic term for satellite navigation systems that provide autonomous geo-spatial positioning with global coverage. This term includes e.g. the GPS, GLONASS, Galileo, Beidou and other regional systems. How does that compare and what are the differences?

GPS

The United States' Global Positioning System (GPS) consists of up to 32 medium Earth orbit satellites in six different orbital planes, with the exact number of satellites varying as older satellites are retired and replaced. Operational since 1978 and globally available since 1994, GPS is currently the world's most utilized satellite navigation system.

By definition, GNSS provides global coverage. Examples of GNSS include Europe’s Galileo, the USA’s NAVSTAR Global Positioning System (GPS), Russia’s Global'naya Navigatsionnaya Sputnikovaya Sistema (GLONASS) and China’s BeiDou Navigation Satellite System.

GNSS/GPS applications include:

- Tracking/Mapping Devices
- Industrial Machinery
- Sea vessels
- Air Navigation
- Automobiles

GPS “Global Positioning System” was the first GNSS system in the United States and originally used for military applications. Today it is commonly used term in agriculture for describing a positioning system that allows us to map fields and auto-steer equipment.

The term GPS is specific to the United States' GNSS system, the NAVSTAR Global Positioning System. The United States NAVSTAR Global Positioning System (GPS) and the Russian GLONASS were the only fully operational GNSS in 2013, hence most people refer to satellite navigation systems as GPS.

The performance of GNSS is assessed using four criteria:

1. Accuracy: the difference between a receiver’s measured and real position, speed or time;

2. Integrity: a system’s capacity to provide a threshold of confidence and, in the event of an anomaly in the positioning data, an alarm;

3. Continuity: a system’s ability to function without interruption;

4. Availability: the percentage of time a signal fulfils the above accuracy, integrity and continuity criteria.

EGNOS

This performance can be improved by regional satellite-based augmentation systems (SBAS), such as the European Geostationary Navigation Overlay Service (EGNOS). EGNOS improves the accuracy and reliability of GPS information by correcting signal measurement errors and by providing information about the integrity of its signals. 

LINKS & REFERENCE

https://velodynelidar.com/

https://www.gsa.europa.eu/egnos/what-egnos

https://www.gsa.europa.eu/european-gnss/what-gnss