Satellite navigation

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The U.S. Space Force's Global Positioning System was the first global satellite navigation system and the first to be provided as a free global service. GPS Block IIIA.jpg
The U.S. Space Force's Global Positioning System was the first global satellite navigation system and the first to be provided as a free global service.

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, five global systems are operational: the United States's Global Positioning System (GPS), Russia's Global Navigation Satellite System (GLONASS), India's Indian Regional Navigation Satellite System (IRNSS), China's BeiDou Navigation Satellite System (BDS), [1] and the European Union's Galileo. [2]

Contents

Satellite-based augmentation systems (SBAS), designed to enhance the accuracy of GNSS, [3] include Japan's Quasi-Zenith Satellite System (QZSS) [3] and the European EGNOS, both based on GPS. Stand-alone operational regional navigation satellite systems (RNSS) include earlier generations of the BeiDou navigation system and the current Indian Regional Navigation Satellite System (IRNSS) or NavIC. [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).

Classification

GNSS systems that provide enhanced accuracy and integrity monitoring usable for civil navigation are classified as follows: [5]

By their roles in the navigation system, systems can be classified as:

As many of the global GNSS systems (and augmentation systems) use similar frequencies and signals around L1, many "Multi-GNSS" receivers capable of using multiple systems have been produced. While some systems strive to interoperate with GPS as well as possible by providing the same clock, others do not. [8]

History

Accuracy of Navigation Systems.svg

Ground based radio navigation is decades old. The DECCA, LORAN, GEE and Omega systems used terrestrial longwave radio transmitters which broadcast a radio pulse from a known "master" location, followed by a pulse repeated from a number of "slave" stations. The delay between the reception of the master signal and the slave signals allowed the receiver to deduce the distance to each of the slaves, providing a fix.

The first satellite navigation system was Transit, a system deployed by the US military in the 1960s. Transit's operation was based on the Doppler effect: the satellites travelled on well-known paths and broadcast their signals on a well-known radio frequency. The received frequency will differ slightly from the broadcast frequency because of the movement of the satellite with respect to the receiver. By monitoring this frequency shift over a short time interval, the receiver can determine its location to one side or the other of the satellite, and several such measurements combined with a precise knowledge of the satellite's orbit can fix a particular position. Satellite orbital position errors are caused by radio-wave refraction, gravity field changes (as the Earth's gravitational field is not uniform), and other phenomena. A team, led by Harold L Jury of Pan Am Aerospace Division in Florida from 1970 to 1973, found solutions and/or corrections for many error sources.[ citation needed ] Using real-time data and recursive estimation, the systematic and residual errors were narrowed down to accuracy sufficient for navigation. [9]

Principles

Part of an orbiting satellite's broadcast includes its precise orbital data. Originally, the US Naval Observatory (USNO) continuously observed the precise orbits of these satellites. As a satellite's orbit deviated, the USNO sent the updated information to the satellite. Subsequent broadcasts from an updated satellite would contain its most recent ephemeris.

Modern systems are more direct. The satellite broadcasts a signal that contains orbital data (from which the position of the satellite can be calculated) and the precise time the signal was transmitted. Orbital data include a rough almanac for all satellites to aid in finding them, and a precise ephemeris for this satellite. The orbital ephemeris is transmitted in a data message that is superimposed on a code that serves as a timing reference. The satellite uses an atomic clock to maintain synchronization of all the satellites in the constellation. The receiver compares the time of broadcast encoded in the transmission of three (at sea level) or four (which allows an altitude calculation also) different satellites, measuring the time-of-flight to each satellite. Several such measurements can be made at the same time to different satellites, allowing a continual fix to be generated in real time using an adapted version of trilateration: see GNSS positioning calculation for details.

Each distance measurement, regardless of the system being used, places the receiver on a spherical shell at the measured distance from the broadcaster. By taking several such measurements and then looking for a point where they meet, a fix is generated. However, in the case of fast-moving receivers, the position of the signal moves as signals are received from several satellites. In addition, the radio signals slow slightly as they pass through the ionosphere, and this slowing varies with the receiver's angle to the satellite, because that changes the distance through the ionosphere. The basic computation thus attempts to find the shortest directed line tangent to four oblate spherical shells centred on four satellites. Satellite navigation receivers reduce errors by using combinations of signals from multiple satellites and multiple correlators, and then using techniques such as Kalman filtering to combine the noisy, partial, and constantly changing data into a single estimate for position, time, and velocity.

Einstein's theory of general relativity is applied to GPS time correction, the net result is that time on a GPS satellite clock advances faster than a clock on the ground by about 38 microseconds per day. [10]

Applications

GNSS satellites used for navigation on a smartphone in 2021 GPSTest GNSS 2021 Android.png
GNSS satellites used for navigation on a smartphone in 2021

The original motivation for satellite navigation was for military applications. Satellite navigation allows precision in the delivery of weapons to targets, greatly increasing their lethality whilst reducing inadvertent casualties from mis-directed weapons. (See Guided bomb). Satellite navigation also allows forces to be directed and to locate themselves more easily, reducing the fog of war.

Now a global navigation satellite system, such as Galileo, is used to determine users location and the location of other people or objects at any given moment. The range of application of satellite navigation in the future is enormous, including both the public and private sectors across numerous market segments such as science, transport, agriculture, insurance, energy, etc. [11] [12]

The ability to supply satellite navigation signals is also the ability to deny their availability. The operator of a satellite navigation system potentially has the ability to degrade or eliminate satellite navigation services over any territory it desires.

Orbit size comparison of GPS, GLONASS, Galileo, BeiDou-2, and Iridium constellations, the International Space Station, the Hubble Space Telescope, and geostationary orbit (and its graveyard orbit), with the Van Allen radiation belts and the Earth to scale. The Moon's orbit is around 9 times as large as geostationary orbit. (In the SVG file, hover over an orbit or its label to highlight it; click to load its article.) Comparison satellite navigation orbits.svg
Orbit size comparison of GPS, GLONASS, Galileo, BeiDou-2, and Iridium constellations, the International Space Station, the Hubble Space Telescope, and geostationary orbit (and its graveyard orbit), with the Van Allen radiation belts and the Earth to scale.
The Moon's orbit is around 9 times as large as geostationary orbit. (In the SVG file, hover over an orbit or its label to highlight it; click to load its article.)
Launched GNSS satellites 1978 to 2014 Launched GNSS 2014.jpg
Launched GNSS satellites 1978 to 2014

In order of first launch year:

GPS

First launch year: 1978

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

GLONASS

First launch year: 1982

The formerly Soviet, and now Russian, Global'naya Navigatsionnaya Sputnikovaya Sistema, (GLObal NAvigation Satellite System or GLONASS), is a space-based satellite navigation system that provides a civilian radionavigation-satellite service and is also used by the Russian Aerospace Defence Forces. GLONASS has full global coverage since 1995 and with 24 active satellites.

BeiDou

First launch year: 2000

BeiDou started as the now-decommissioned Beidou-1, an Asia-Pacific local network on the geostationary orbits. The second generation of the system BeiDou-2 became operational in China in December 2011. [13] The BeiDou-3 system is proposed to consist of 30 MEO satellites and five geostationary satellites (IGSO). A 16-satellite regional version (covering Asia and Pacific area) was completed by December 2012. Global service was completed by December 2018. [14] On 23 June 2020, the BDS-3 constellation deployment is fully completed after the last satellite was successfully launched at the Xichang Satellite Launch Center. [15]

Galileo

First launch year: 2011

The European Union and European Space Agency agreed in March 2002 to introduce their own alternative to GPS, called the Galileo positioning system. Galileo became operational on 15 December 2016 (global Early Operational Capability, EOC). [16] At an estimated cost of €10 billion, [17] the system of 30 MEO satellites was originally scheduled to be operational in 2010. The original year to become operational was 2014. [18] The first experimental satellite was launched on 28 December 2005. [19] Galileo is expected to be compatible with the modernized GPS system. The receivers will be able to combine the signals from both Galileo and GPS satellites to greatly increase the accuracy. The full Galileo constellation consists of 24 active satellites, [20] the last of which was launched in December 2021. [21] [22] The main modulation used in Galileo Open Service signal is the Composite Binary Offset Carrier (CBOC) modulation.

Regional navigation satellite systems

The NavIC or NAVigation with Indian Constellation is an autonomous regional satellite navigation system developed by the Indian Space Research Organisation (ISRO). The Indian government approved the project in May 2006. It consists of a constellation of 7 navigational satellites. [23] Three of the satellites are placed in geostationary orbit (GEO) and the remaining 4 in geosynchronous orbit (GSO) to have a larger signal footprint and lower number of satellites to map the region. It is intended to provide an all-weather absolute position accuracy of better than 7.6 metres (25 ft) throughout India and within a region extending approximately 1,500 km (930 mi) around it. [24] An Extended Service Area lies between the primary service area and a rectangle area enclosed by the 30th parallel south to the 50th parallel north and the 30th meridian east to the 130th meridian east, 1,500–6,000 km beyond borders. [25] A goal of complete Indian control has been stated, with the space segment, ground segment and user receivers all being built in India. [26]

The constellation was in orbit as of 2018, and the system was available for public use in early 2018. [27] NavIC provides two levels of service, the "standard positioning service", which will be open for civilian use, and a "restricted service" (an encrypted one) for authorized users (including military). There are plans to expand NavIC system by increasing constellation size from 7 to 11. [28]

India plans to make the NAVIC global by adding 24 more MEO satellites. The Global NavIC will be free to use for the global public. [29]

Early BeiDou

The first two generations of China's BeiDou navigation system were designed to provide regional coverage.

Augmentation

GNSS augmentation is a method of improving a navigation system's attributes, such as accuracy, reliability, and availability, through the integration of external information into the calculation process, for example, the Wide Area Augmentation System, the European Geostationary Navigation Overlay Service, the Multi-functional Satellite Augmentation System, Differential GPS, GPS-aided GEO augmented navigation (GAGAN) and inertial navigation systems.

QZSS

The Quasi-Zenith Satellite System (QZSS) is a four-satellite regional time transfer system and enhancement for GPS covering Japan and the Asia-Oceania regions. QZSS services were available on a trial basis as of January 12, 2018, and were started in November 2018. The first satellite was launched in September 2010. [30] An independent satellite navigation system (from GPS) with 7 satellites is planned for 2023. [31]

EGNOS

This section is an excerpt from European Geostationary Navigation Overlay Service.[ edit ]
Map of the EGNOS ground network EGNOS map.svg
Map of the EGNOS ground network

The European Geostationary Navigation Overlay Service (EGNOS) is a satellite-based augmentation system (SBAS) developed by the European Space Agency and EUROCONTROL on behalf of the European Commission. Currently, it supplements the GPS by reporting on the reliability and accuracy of their positioning data and sending out corrections. The system will supplement Galileo in a future version.

EGNOS consists of 40 Ranging Integrity Monitoring Stations, 2 Mission Control Centres, 6 Navigation Land Earth Stations, the EGNOS Wide Area Network (EWAN), and 3 geostationary satellites. [32] Ground stations determine the accuracy of the satellite navigation systems data and transfer it to the geostationary satellites; users may freely obtain this data from those satellites using an EGNOS-enabled receiver, or over the Internet. One main use of the system is in aviation.

According to specifications, horizontal position accuracy when using EGNOS-provided corrections should be better than seven metres. In practice, the horizontal position accuracy is at the metre level.

Similar service is provided in North America by the Wide Area Augmentation System (WAAS), in Russia by the System for Differential Corrections and Monitoring (SDCM), and in Asia, by Japan's Multi-functional Satellite Augmentation System (MSAS) and India's GPS-aided GEO augmented navigation (GAGAN).

Galileo and EGNOS budget for the 2021–2027 period is €9 billion [33]

Comparison of systems

System BeiDou Galileo GLONASS GPS NavIC QZSS
Owner China European Union Russia United States India Japan
CoverageGlobalGlobalGlobalGlobalRegionalRegional
Coding CDMA CDMA FDMA & CDMA CDMA CDMA CDMA
Altitude21,150 km (13,140 mi)23,222 km (14,429 mi)19,130 km (11,890 mi)20,180 km (12,540 mi)36,000 km (22,000 mi)32,600 km (20,300 mi) –
39,000 km (24,000 mi) [34]
Period12.88 h (12 h 53 min)14.08 h (14 h  5 min)11.26 h (11 h 16 min)11.97 h (11 h 58 min)23.93 h (23 h 56 min)23.93 h (23 h 56 min)
Rev./S. day 13/7 (1.86)17/10 (1.7)17/8 (2.125)211
SatellitesBeiDou-3:
28 operational
(24 MEO, 3 IGSO, 1 GSO)
5 in orbit validation
2 GSO planned 20H1
BeiDou-2:
15 operational
1 in commissioning		By design:

27 operational + 3 spares

Currently:

26 in orbit
24 operational

2 inactive
6 to be launched [35]

24 by design
24 operational
1 commissioning
1 in flight tests [36] 		24 by design
30 operational [37] 		8 operational
(3 GEO, 5 GSO MEO)		4 operational (3 GSO, 1 GEO)
7 in the future
Frequency1.561098 GHz (B1)
1.589742 GHz (B1-2)
1.20714 GHz (B2)
1.26852 GHz (B3)		1.559–1.592 GHz (E1)
1.164–1.215 GHz (E5a/b)
1.260–1.300 GHz (E6)		1.593–1.610 GHz (G1)
1.237–1.254 GHz (G2)
1.189–1.214 GHz (G3)		1.563–1.587 GHz (L1)
1.215–1.2396 GHz (L2)
1.164–1.189 GHz (L5)		1.17645 GHz(L5)
2.492028 GHz (S)		1.57542 GHz (L1C/A, L1C, L1S)
1.22760 GHz (L2C)
1.17645 GHz (L5, L5S)
1.27875 GHz (L6) [38]
StatusOperational [39] Operating since 2016
2020 completion [35] 		OperationalOperationalOperationalOperational
Accuracy3.6 metres (12 ft) (public)
0.1 metres (0.33 ft) (encrypted)		0.2 metres (0.66 ft) (public)
0.01 metres (0.033 ft) (encrypted)		2–4 metres (6.6–13.1 ft)0.3–5 metres (0.98–16.40 ft)
(no DGPS or WAAS)		1 metre (3.3 ft) (public)
0.1 metres (0.33 ft) (encrypted)		1 metre (3.3 ft) (public)
0.1 metres (0.33 ft) (encrypted)
System BeiDou Galileo GLONASS GPS NavIC QZSS

Sources: [7] [40]

Using multiple GNSS systems for user positioning increases the number of visible satellites, improves precise point positioning (PPP) and shortens the average convergence time. [41] The signal-in-space ranging error (SISRE) in November 2019 were 1.6 cm for Galileo, 2.3 cm for GPS, 5.2 cm for GLONASS and 5.5 cm for BeiDou when using real-time corrections for satellite orbits and clocks. [42] The average SISREs of the BDS-3 MEO, IGSO, and GEO satellites were 0.52 m, 0.90 m and 1.15 m, respectively. Compared to the four major global satellite navigation systems consisting of MEO satellites, the SISRE of the BDS-3 MEO satellites was slightly inferior to 0.4 m of Galileo, slightly superior to 0.59 m of GPS, and remarkably superior to 2.33 m of GLONASS. The SISRE of BDS-3 IGSO was 0.90 m, which was on par with the 0.92 m of QZSS IGSO. However, as the BDS-3 GEO satellites were newly launched and not completely functioning in orbit, their average SISRE was marginally worse than the 0.91 m of the QZSS GEO satellites. [3]

DORIS

Doppler Orbitography and Radio-positioning Integrated by Satellite (DORIS) is a French precision navigation system. Unlike other GNSS systems, it is based on static emitting stations around the world, the receivers being on satellites, in order to precisely determine their orbital position. The system may be used also for mobile receivers on land with more limited usage and coverage. Used with traditional GNSS systems, it pushes the accuracy of positions to centimetric precision (and to millimetric precision for altimetric application and also allows monitoring very tiny seasonal changes of Earth rotation and deformations), in order to build a much more precise geodesic reference system. [43]

LEO satellites

The two current operational low Earth orbit (LEO) satellite phone networks are able to track transceiver units with accuracy of a few kilometres using doppler shift calculations from the satellite. The coordinates are sent back to the transceiver unit where they can be read using AT commands or a graphical user interface. [44] [45] This can also be used by the gateway to enforce restrictions on geographically bound calling plans.

International regulation

The International Telecommunication Union (ITU) defines a radionavigation-satellite service (RNSS) as "a radiodetermination-satellite service used for the purpose of radionavigation. This service may also include feeder links necessary for its operation". [46]

RNSS is regarded as a safety-of-life service and an essential part of navigation which must be protected from interferences.

Aeronautical radionavigation-satellite (short: ARNSS) is – according to Article 1.47 of the International Telecommunication Union's (ITU) Radio Regulations (RR) [47] – defined as «A radionavigation service in which earth stations are located on board aircraft.»

Maritime radionavigation-satellite service (short: MRNSS) is – according to Article 1.45 of the International Telecommunication Union's (ITU) Radio Regulations (RR) [48] – defined as «A radionavigation-satellite service in which earth stations are located on board ships.»

Classification

ITU Radio Regulations (article 1) classifies radiocommunication services as:

Examples of RNSS use

Frequency allocation

The allocation of radio frequencies is provided according to Article 5 of the ITU Radio Regulations (edition 2012). [49]

To improve harmonisation in spectrum utilisation, most service allocations are incorporated in national Tables of Frequency Allocations and Utilisations within the responsibility of the appropriate national administration. Allocations are:

Allocation to services
Region 1      Region 2          Region 3     
5 000–5 010 MHz
AERONAUTICAL MOBILE-SATELLITE (R)
AERONAUTICAL RADIONAVIGATION
RADIONAVIGATION-SATELLITE (Earth-to-space)

See also

Notes

  1. ↑ Orbital periods and speeds are calculated using the relations 4π2R3 = T2GM and V2R = GM, where R is the radius of orbit in metres; T is the orbital period in seconds; V is the orbital speed in m/s; G is the gravitational constant, approximately 6.673×10−11 Nm2/kg2; M is the mass of Earth, approximately 5.98×1024 kg (1.318×1025 lb).
  2. ↑ Approximately 8.6 times (in radius and length) when the Moon is nearest (that is, 363,104 km/42,164 km), to 9.6 times when the Moon is farthest (that is, 405,696 km/42,164 km).

Related Research Articles

<span class="mw-page-title-main">Global Positioning System</span> American satellite-based radio navigation service

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.

<span class="mw-page-title-main">Galileo (satellite navigation)</span> Global navigation satellite system

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.

<span class="mw-page-title-main">GLONASS</span> Russian satellite navigation 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.

<span class="mw-page-title-main">Radio navigation</span> Use of radio-frequency electromagnetic waves to determine position on the Earths surface

Radio navigation or radionavigation is the application of radio frequencies to determine a position of an object on the Earth, either the vessel or an obstruction. Like radiolocation, it is a type of radiodetermination.

Global air-traffic management (GATM) is a concept for satellite-based Communication, navigation and surveillance and air traffic management. The Federal Aviation Administration and the International Civil Aviation Organization, a specialized agency of the United Nations, established GATM standards to keep air travel safe and effective in increasingly crowded worldwide air space. Efforts are being made worldwide to test and implement new technologies that will allow GATM to efficiently support air traffic control.

<span class="mw-page-title-main">European Geostationary Navigation Overlay Service</span> System that enhances the accuracy of GPS receivers

The European Geostationary Navigation Overlay Service (EGNOS) is a satellite-based augmentation system (SBAS) developed by the European Space Agency and EUROCONTROL on behalf of the European Commission. Currently, it supplements the GPS by reporting on the reliability and accuracy of their positioning data and sending out corrections. The system will supplement Galileo in a future version.

<span class="mw-page-title-main">BeiDou</span> Chinese satellite navigation system

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 (GNSS) 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.

<span class="mw-page-title-main">Wide Area Augmentation System</span> System that enhances the accuracy of GPS receivers

The Wide Area Augmentation System (WAAS) is an air navigation aid developed by the Federal Aviation Administration to augment the Global Positioning System (GPS), with the goal of improving its accuracy, integrity, and availability. Essentially, WAAS is intended to enable aircraft to rely on GPS for all phases of flight, including precision approaches to any airport within its coverage area. It may be further enhanced with the Local Area Augmentation System (LAAS) also known by the preferred ICAO term Ground-Based Augmentation System (GBAS) in critical areas.

<span class="mw-page-title-main">Assisted GNSS</span> System to improve the time-to-first-fix of a GNSS receiver

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.

<span class="mw-page-title-main">Differential GPS</span> Enhancement to the Global Positioning System providing improved accuracy

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.

<span class="mw-page-title-main">Real-time kinematic positioning</span> Satellite navigation technique used to enhance the precision of position data

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.

<span class="mw-page-title-main">International Cospas-Sarsat Programme</span> International satellite-aided search and rescue initiative

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.

<span class="mw-page-title-main">Quasi-Zenith Satellite System</span> Navigation satellites

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.

Multi-functional Satellite Augmentation System is a Japanese satellite based augmentation system (SBAS), i.e. a satellite navigation system which supports differential GPS (DGPS) to supplement the GPS system by reporting on the reliability and accuracy of those signals. MSAS is operated by Japan's Ministry of Land, Infrastructure and Transport and Civil Aviation Bureau (JCAB). Tests have been accomplished successfully, MSAS for aviation use was commissioned on 27 September 2007.

The GPS-aided GEO augmented navigation (GAGAN) is an implementation of a regional satellite-based augmentation system (SBAS) by the Government of India. It is a system to improve the accuracy of a GNSS receiver by providing reference signals. The Airports Authority of India (AAI)'s efforts towards implementation of operational SBAS can be viewed as the first step towards introduction of modern communication, navigation and surveillance / air traffic management system over the Indian airspace.

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.

In the field of geodesy, Receiver Independent Exchange Format (RINEX) is a data interchange format for raw satellite navigation system data. This allows the user to post-process the received data to produce a more accurate result — usually with other data unknown to the original receiver, such as better models of the atmospheric conditions at time of measurement.

A software GNSS receiver is a Global Navigation Satellite System (GNSS) receiver that has been designed and implemented using software-defined radio.

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.

<span class="mw-page-title-main">U-blox</span>

u-blox is a Swiss company that creates wireless semiconductors and modules for consumer, automotive and industrial markets. They operate as a fabless IC and design house. The company is listed at the Swiss Stock Exchange (SIX:UBXN) and has offices in the US, Singapore, China, Taiwan, Korea, Japan, India, Pakistan, Australia, Ireland, the UK, Belgium, Germany, Sweden, Finland, Italy and Greece.

References

  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.
  3. 1 2 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.
  5. 1 2 3 4 "A Beginner's Guide to GNSS in Europe" (PDF). IFATCA. Archived from the original (PDF) on 27 June 2017. Retrieved 20 May 2015.
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  30. ↑ "About QZSS". JAXA. Archived from the original on 2009-03-14. Retrieved 2009-02-22.
  31. ↑ Henry, Caleb (15 May 2017). "Japan mulls seven-satellite QZSS system as a GPS backup". SpaceNews.com. Archived from the original on 9 Dec 2023. Retrieved 10 August 2019.
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  46. ↑ ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.43, definition: radionavigation-satellite service
  47. ↑ ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.47, definition: aeronautical radionavigation service
  48. ↑ ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.45, definition: maritime radionavigation-satellite service
  49. ↑ ITU Radio Regulations, CHAPTER II – Frequencies, ARTICLE 5 Frequency allocations, Section IV – Table of Frequency Allocations

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