Satellite navigation

Satellite navigation (satnav) or satellite positioning is the use of artificial satellites for navigation or geopositioning. A global navigation satellite system (GNSS) provides coverage for any user on Earth, including air, land, and sea. There are four operational GNSS systems: the United States Global Positioning System (GPS), Russia's Global Navigation Satellite System (GLONASS), China's BeiDou Navigation Satellite System (BDS),^[1] and the European Union's Galileo.^[2]

A satellite-based augmentation system (SBAS) is a system that designed to enhance the accuracy of the global GNSS systems.^[3] The SBAS systems include Japan's Quasi-Zenith Satellite System (QZSS),^[3] India's GAGAN, and the European EGNOS, all of them based on GPS. Previous iterations of the BeiDou navigation system and the present Indian Regional Navigation Satellite System (IRNSS), operationally known as NavIC, are examples of stand-alone operating regional navigation satellite systems (RNSS).^[4]

Satellite navigation devices determine their location (longitude, latitude, and altitude/elevation) to high precision (within a few centimeters to meters) using time signals transmitted along a line of sight by radio from satellites. The system can be used for providing position, navigation or for tracking the position of something fitted with a receiver (satellite tracking). The signals also allow the electronic receiver to calculate the current local time to a high precision, which allows time synchronisation. These uses are collectively known as Positioning, Navigation and Timing (PNT). Satnav systems operate independently of any telephonic or internet reception, though these technologies can enhance the usefulness of the positioning information generated.

Global coverage for each system is generally achieved by a satellite constellation of 18–30 medium Earth orbit (MEO) satellites spread between several orbital planes. The actual systems vary, but all use orbital inclinations of >50° and orbital periods of roughly twelve hours (at an altitude of about 20,000 kilometres or 12,000 miles).

^ "China's GPS rival Beidou is now fully operational after final satellite launched". cnn.com. 24 June 2020. Retrieved 2020-06-26.
^ "Galileo is the European global satellite-based navigation system". www.euspa.europa.eu. 26 January 2024. Retrieved 26 January 2024.
^ ^a ^b Kriening, Torsten (23 January 2019). "Japan Prepares for GPS Failure with Quasi-Zenith Satellites". SpaceWatch.Global. Retrieved 10 August 2019.
^ Indian Satellite Navigation Policy - 2021 (Draft) (PDF). Bengaluru, India: Department of Space. 2021. p. 7. Archived from the original (PDF) on 30 July 2021. Retrieved 27 July 2022. ISRO/DOS shall work towards expanding the coverage from regional to global to ensure availability of NavIC standalone signal in any part of the world without relying on other GNSS and aid in wide utilisation of Indian navigation system across the globe.

[autogenerated1-1] "China's GPS rival Beidou is now fully operational after final satellite launched". cnn.com. 24 June 2020. Retrieved 2020-06-26.

[2] "Galileo is the European global satellite-based navigation system". www.euspa.europa.eu. 26 January 2024. Retrieved 26 January 2024.

[:1-3] Kriening, Torsten (23 January 2019). "Japan Prepares for GPS Failure with Quasi-Zenith Satellites". SpaceWatch.Global. Retrieved 10 August 2019.

[4] Indian Satellite Navigation Policy - 2021 (Draft) (PDF). Bengaluru, India: Department of Space. 2021. p. 7. Archived from the original (PDF) on 30 July 2021. Retrieved 27 July 2022. ISRO/DOS shall work towards expanding the coverage from regional to global to ensure availability of NavIC standalone signal in any part of the world without relying on other GNSS and aid in wide utilisation of Indian navigation system across the globe.

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