The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radio navigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite systems (GNSS) that provide geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. It does not require the user to transmit any data, and operates independently of any telephonic or Internet reception, though these technologies can enhance the usefulness of the GPS positioning information. It provides critical positioning capabilities to military, civil, and commercial users around the world. Although the United States government created, controls and maintains the GPS system, it is freely accessible to anyone with a GPS receiver.
Galileo is a global navigation satellite system (GNSS) that went live in 2016, created by the European Union through the European Space Agency (ESA), operated by the European Union Agency for the Space Programme (EUSPA), headquartered in Prague, Czechia, with two ground operations centres in Fucino, Italy, and Oberpfaffenhofen, Germany. The €10 billion project is named after the Italian astronomer Galileo Galilei. One of the aims of Galileo is to provide an independent high-precision positioning system so European political and military authorities do not have to rely on the US GPS, or the Russian GLONASS systems, which could be disabled or degraded by their operators at any time. The use of basic (lower-precision) Galileo services is free and open to everyone. A fully encrypted higher-precision service is available for free to government-authorized users. Galileo is intended to provide horizontal and vertical position measurements within 1 m precision. Galileo is also to provide a new global search and rescue (SAR) function as part of the MEOSAR system.
GLONASS is a Russian satellite navigation system operating as part of a radionavigation-satellite service. It provides an alternative to Global Positioning System (GPS) and is the second navigational system in operation with global coverage and of comparable precision.
Time and frequency transfer is a scheme where multiple sites share a precise reference time or frequency. The technique is commonly used for creating and distributing standard time scales such as International Atomic Time (TAI). Time transfer solves problems such as astronomical observatories correlating observed flashes or other phenomena with each other, as well as cell phone towers coordinating handoffs as a phone moves from one cell to another.
The BeiDou Navigation Satellite System is a satellite-based radio navigation system owned and operated by the China National Space Administration. It is one of the global navigation satellite systems that provide geolocation and time information to a BDS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more BDS satellites. It does not require the user to transmit any data, and operates independently of any telephonic or Internet reception, though these technologies can enhance the usefulness of the BDS positioning information.
In the context of information security, and especially network security, a spoofing attack is a situation in which a person or program successfully identifies as another by falsifying data, to gain an illegitimate advantage.
Assisted GNSS (A-GNSS) is a GNSS augmentation system that often significantly improves the startup performance—i.e., time-to-first-fix (TTFF)—of a global navigation satellite system (GNSS). A-GNSS works by providing the necessary data to the device via a radio network instead of the slow satellite link, essentially "warming up" the receiver for a fix. When applied to GPS, it is known as assisted GPS or augmented GPS. Other local names include A-GANSS for Galileo and A-Beidou for BeiDou.
A satellite navigation or satnav system is a system that uses satellites to provide autonomous geopositioning. A satellite navigation system with global coverage is termed global navigation satellite system (GNSS). As of 2023, four global systems are operational: the United States’s Global Positioning System (GPS), Russia's Global Navigation Satellite System (GLONASS), China's BeiDou Navigation Satellite System, and the European Union's Galileo.
Differential Global Positioning Systems (DGPSs) supplement and enhance the positional data available from global navigation satellite systems (GNSSs). A DGPS for GPS can increase accuracy by about a thousandfold, from approximately 15 metres (49 ft) to 1–3 centimetres.
Real-time kinematic positioning (RTK) is the application of surveying to correct for common errors in current satellite navigation (GNSS) systems. It uses measurements of the phase of the signal's carrier wave in addition to the information content of the signal and relies on a single reference station or interpolated virtual station to provide real-time corrections, providing up to centimetre-level accuracy. With reference to GPS in particular, the system is commonly referred to as carrier-phase enhancement, or CPGPS. It has applications in land surveying, hydrographic surveying, and in unmanned aerial vehicle navigation.
The International Cospas-Sarsat Programme is a satellite-aided search and rescue (SAR) initiative. It is organized as a treaty-based, nonprofit, intergovernmental, humanitarian cooperative of 45 nations and agencies. It is dedicated to detecting and locating emergency locator radio beacons activated by persons, aircraft or vessels in distress, and forwarding this alert information to authorities that can take action for rescue. Member countries support the distribution of distress alerts using a constellation of around 65 satellites orbiting the Earth which carry transponders and signal processors capable of locating an emergency beacon anywhere on Earth transmitting on the Cospas-Sarsat frequency of 406 MHz.
The Quasi-Zenith Satellite System (QZSS), also known as Michibiki (みちびき), is a four-satellite regional satellite navigation system and a satellite-based augmentation system developed by the Japanese government to enhance the United States-operated Global Positioning System (GPS) in the Asia-Oceania regions, with a focus on Japan. The goal of QZSS is to provide highly precise and stable positioning services in the Asia-Oceania region, compatible with GPS. Four-satellite QZSS services were available on a trial basis as of 12 January 2018, and officially started on 1 November 2018. A satellite navigation system independent of GPS is planned for 2023 with seven satellites. In May 2023 it was announced that the system would expand to eleven satellites.
GNSS reflectometry involves making measurements from the reflections from the Earth of navigation signals from Global Navigation Satellite Systems such as GPS. The idea of using reflected GNSS signal for earth observation became more and more popular in the mid-1990s at NASA Langley Research Center and is also known as GPS reflectometry. Research applications of GNSS-R are found in
Augmentation of a global navigation satellite system (GNSS) is a method of improving the navigation system's attributes, such as precision, reliability, and availability, through the integration of external information into the calculation process. There are many such systems in place, and they are generally named or described based on how the GNSS sensor receives the external information. Some systems transmit additional information about sources of error, others provide direct measurements of how much the signal was off in the past, while a third group provides additional vehicle information to be integrated in the calculation process.
Global Navigation Satellite System (GNSS) receivers, using the GPS, GLONASS, Galileo or BeiDou system, are used in many applications. The first systems were developed in the 20th century, mainly to help military personnel find their way, but location awareness soon found many civilian applications.
A satellite navigation device, satnav device or satellite navigation receiver is a user equipment that uses one or more of several global navigation satellite systems (GNSS) to calculate the device's geographical position and provide navigational advice. Depending on the software used, the satnav device may display the position on a map, as geographic coordinates, or may offer routing directions.
A software GNSS receiver is a Global Navigation Satellite System (GNSS) receiver that has been designed and implemented using software-defined radio.
RACELOGIC Ltd is a technology company based in Buckingham, United Kingdom.
Inside GNSS (IG) is an international controlled circulation trade magazine and website owned by Gibbons Media and Research LLC. It covers space-based positioning, navigation and timing (PNT) technology for engineers, designers, and policy-makers of global navigation satellite systems (GNSS). In the United States, GNSS is identified mainly with the government-operated Navstar Global Positioning System (GPS). InsideGNSS.com is the complimentary website of online news, events, digital newsletters, and webinars, and archived magazine articles.
GPS Block IIIF, or GPS III Follow On (GPS IIIF), is the second set of GPS Block III satellites, consisting of up to 22 space vehicles. The United States Air Force began the GPS Block IIIF acquisition effort in 2016. On 14 September 2018, a manufacturing contract with options worth up to $7.2 billion was awarded to Lockheed Martin. The 22 satellites in Block IIIF are projected to start launching in 2027, with launches estimated to last through at least 2034.
