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A satellite navigation device (satnav device) is a user equipment that uses one or more of several
global navigation satellite systems A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows satellite navigation devices to determine their location (longitude, latitude, and altitude/elevation) to high pr ...
(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 The geographic coordinate system (GCS) is a spherical or ellipsoidal coordinate system for measuring and communicating positions directly on the Earth as latitude and longitude. It is the simplest, oldest and most widely used of the various ...
, or may offer routing directions. As of September 2020, there were four operational GNSS systems, the original United States'
Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
(GPS), the European Union's Galileo, Russia's
GLONASS GLONASS (russian: ГЛОНАСС, label=none, ; rus, links=no, Глобальная навигационная спутниковая система, r=Global'naya Navigatsionnaya Sputnikovaya Sistema, t=Global Navigation Satellite System) is ...
, and China's
BeiDou The BeiDou Navigation Satellite System (BDS; ) is a Chinese satellite navigation system. It consists of two separate satellite constellations. The first BeiDou system, officially called the BeiDou Satellite Navigation Experimental System and ...
Navigation Satellite System. The
Indian Regional Navigation Satellite System The Indian Regional Navigation Satellite System (IRNSS), with an operational name of NavIC (acronym for 'Navigation with Indian Constellation; also, 'sailor' or 'navigator' in Indian languages), is an autonomous regional satellite navigation s ...
(IRNSS) will follow and Japan's
Quasi-Zenith Satellite System The Quasi-Zenith Satellite System (QZSS), also known as , is a four-satellite regional time transfer system and a satellite-based augmentation system developed by the Japanese government to enhance the United States-operated Global Position ...
(
QZSS The Quasi-Zenith Satellite System (QZSS), also known as , is a four-satellite regional time transfer system and a satellite-based augmentation system developed by the Japanese government to enhance the United States-operated Global Position ...
) scheduled for 2023 will augment the accuracy of a number of GNSS. A satellite navigation device can retrieve location and time information from one or more GNSS systems in all weather conditions, anywhere on or near the Earth's surface. Satnav reception requires an unobstructed line of sight to four or more GNSS satellites, and is subject to poor satellite signal conditions. In exceptionally poor signal conditions, for example in urban areas, satellite signals may exhibit multipath propagation where signals bounce off structures, or are weakened by meteorological conditions. Obstructed lines of sight may arise from a tree canopy or inside a structure, such as in a building, garage or tunnel. Today, most standalone Satnav receivers are used in automobiles. The Satnav capability of
smartphone A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...
s may use
assisted GNSS 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 ...
(A-GNSS) technology, which can use the base station or
cell tower A cell site, cell tower, or cellular base station is a cellular-enabled mobile device site where antennas and electronic communications equipment are placed (typically on a radio mast, tower, or other raised structure) to create a cell, or adj ...
s to provide a faster Time to First Fix (TTFF), especially when satellite signals are poor or unavailable. However, the mobile network part of the A-GNSS technology would not be available when the smartphone is outside the range of the mobile reception network, while the satnav aspect would otherwise continue to be available.


Vehicle navigation system

An automotive navigation system takes its location from a GNSS system and, depending on the installed software, may offer the following services: * Mapping, including street maps, text or in a graphical format, *
Turn-by-turn navigation Turn-by-turn Navigation is a feature of some satellite navigation devices where directions for a selected route are continually presented to the user in the form of spoken or visual instructions. The system keeps the user up-to-date about the best ...
directions via text or speech, * Directions fed directly to a
self-driving car A self-driving car, also known as an autonomous car, driver-less car, or robotic car (robo-car), is a car that is capable of traveling without human input.Xie, S.; Hu, J.; Bhowmick, P.; Ding, Z.; Arvin, F.,Distributed Motion Planning for S ...
, * Traffic congestion maps, historical or real-time data, and suggested alternative directions, * Information on nearby amenities such as restaurants, fueling stations, and tourist attractions, * Alternative routes.


History

As with many other technological breakthroughs of the latter 20th century, the modern GNSS system can reasonably be argued to be a direct outcome of the Cold War of the latter 20th century. The multibillion-dollar expense of the US and Russian programs was initially justified by military interest. In contrast, the European Galileo was conceived as purely civilian. In 1960, the US Navy put into service its
Transit Transit may refer to: Arts and entertainment Film * ''Transit'' (1979 film), a 1979 Israeli film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countries in the world * ''Transit'' (2006 film), a 2006 ...
satellite-based navigation system to aid in naval navigation. The US Navy in the mid-1960s conducted an experiment to track a submarine with missiles with six satellites and orbiting poles and was able to observe satellite changes. Between 1960 and 1982, as the benefits were shown, the US military consistently improved and refined its satellite navigation technology and satellite system. In 1973, the US military began to plan for a comprehensive worldwide navigational system which eventually became known as the GPS (Global Positioning System). In 1983, in the wake of the tragedy of the downing of
Korean Air Lines Flight 007 Korean Air Lines Flight 007 (KE007/KAL007)The flight number KAL 007 was used by air traffic control, while the public flight booking system used KE 007 was a scheduled Korean Air Lines flight from New York City to Seoul via Anchorage, Alas ...
, an aircraft which was shot down while in Soviet airspace due to a navigational error, President Ronald Reagan made the navigation capabilities of the existing military GPS system available for dual civilian use. However, civilian use was initially only a slightly degraded "
Selective Availability The error analysis for the Global Positioning System is important for understanding how GPS works, and for knowing what magnitude of error should be expected. The GPS makes corrections for receiver clock errors and other effects but there are sti ...
" positioning signal. This new availability of the US military GPS system for civilian use required a certain technical collaboration with the private sector for some time, before it could become a commercial reality. In 1989, Magellan Navigation Inc. unveiled its Magellan NAV 1000, the world's first commercial handheld GPS receiver. These units initially sold for approximately US$2,900 each. In 2000, the Clinton administration removed the military use signal restrictions, thus providing full commercial access to the US Satnav satellite system. In 1990,
Mazda , commonly referred to as simply Mazda, is a Japanese multinational automotive manufacturer headquartered in Fuchū, Hiroshima, Japan. In 2015, Mazda produced 1.5 million vehicles for global sales, the majority of which (nearly one m ...
's
Eunos Cosmo The is an automobile which was produced by Mazda from 1967 until 1995. Throughout its history, the Cosmo served as a "halo" vehicle for Mazda, with the first Cosmo successfully launching the Mazda Wankel engine. The final generation of Cosmo ser ...
was the first production car in the world with a built-in Satnav system. In 1991, Mitsubishi introduced Satnav car navigation on the
Mitsubishi Debonair The is a four-door executive sedan introduced by Mitsubishi Motors in 1964 to serve as their flagship passenger vehicle in the Japanese market. The word "debonair" means gentle, courteous, suave, lighthearted, or nonchalant. __TOC__ Overvi ...
(MMCS: Mitsubishi Multi Communication System). In 1997, a navigation system using
Differential GPS 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 to . DGPSs c ...
was developed as a factory-installed option on the
Toyota Prius The is a car built by Toyota which has a hybrid drivetrain, combining an internal combustion engine with an electric motor. Initially offered as a four-door sedan, it has been produced only as a five-door liftback since 2003. In 2007, ...
. As GNSS navigation systems became more and more widespread and popular, the pricing of such systems began to fall, and their widespread availability steadily increased. Also, several additional manufacturers of these systems, such as
Garmin Garmin Ltd. (shortened to Garmin, stylized as GARMIN, and formerly known as ProNav) is an American, Swiss-domiciled multinational technology company founded in 1989 by Gary Burrell and Min Kao in Lenexa, Kansas, United States, with headquarte ...
(1991), Benefon (1999),
Mio Mio or MIO may refer to: shortened form of Mioritic Shepherd dog or Mioritic sheepdog; a Romanian mountain dog. Places * Mio, Michigan, a town in the US Music * ''Mío'', 2011 album by David Bustamante * "Mío", 1992 song by Paulina Rubio Bra ...
(2002) and
TomTom TomTom N.V. is a Dutch multinational developer and creator of location technology and consumer electronics. Founded in 1991 and headquartered in Amsterdam, TomTom released its first generation of satellite navigation devices to market in 2004. ...
(2002) entered the market. Mitac Mio 168 was the first PocketPC to contain a built-in GPS receiver. Benefon's 1999 entry into the market also presented users with the world's first phone based GPS navigation system. Later, as smartphone technology developed, a GPS chip eventually became standard equipment for most smartphones. To date, ever more popular satellite navigation systems and devices continue to proliferate with newly developed software and hardware applications. It has been incorporated, for example, into cameras. While the American GPS was the first
satellite navigation A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows satellite navigation devices to determine their location (longitude, latitude, and altitude/elevation) to high pr ...
system to be deployed on a fully global scale, and to be made available for commercial use, this is not the only system of its type. Due to military and other concerns, similar global or regional systems have been, or will soon be deployed by Russia, the European Union, China, India, and Japan. GNSS have made many strides into today's world. It can now help out in things such as parents now using GNSS devices to attach to their kids to monitor their movement and always know their location. Also helps out with detecting the movements and behavior of animals and also helps officers with car chases and not having to chase exactly behind a criminal and lastly using GPS bullets to catch criminals. The ''Macrometer Interferometric Surveyor'' was the first commercial GNSS-based system for performing
geodetic Geodesy ( ) is the Earth science of accurately measuring and understanding Earth's figure (geometric shape and size), orientation in space, and gravity. The field also incorporates studies of how these properties change over time and equivale ...
measurements.


Sensitivity

GNSS devices vary in sensitivity, speed, vulnerability to multipath propagation, and other performance parameters. High-sensitivity receivers use large banks of correlators and digital signal processing to search for signals very quickly. This results in very fast times to first fix when the signals are at their normal levels, for example, outdoors. When signals are weak, for example, indoors, the extra processing power can be used to integrate weak signals to the point where they can be used to provide a position or timing solution. GNSS signals are already very weak when they arrive at the Earth's surface. The
GPS satellite GPS satellite blocks are the various production generations of the Global Positioning System (GPS) used for satellite navigation. The first satellite in the system, Navstar 1, was launched on 22 February 1978. The GPS satellite constellatio ...
s only transmit 27 W (14.3 dBW) from a distance of 20,200 km in
orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...
above the Earth. By the time the signals arrive at the user's receiver, they are typically as weak as −160  dBW, equivalent to 100 attowatts (10−16 W). This is well below the thermal noise level in its bandwidth. Outdoors, GPS signals are typically around the −155 dBW level (−125 
dBm DBM or dbm may refer to: Science and technology * dBm, a unit for power measurement * DBM (computing), family of key-value database engines including dbm, ndbm, gdbm, and Berkeley DB * Database Manager (DBM), a component of 1987's ''Extended Edi ...
). Conventional GPS receivers integrate the received GPS signals for the same amount of time as the duration of a complete C/A code cycle which is 1 ms. This results in the ability to acquire and track signals down to around the −160 dBW level. High-sensitivity GPS receivers are able to integrate the incoming signals for up to 1,000 times longer than this and therefore acquire signals up to 1,000 times weaker, resulting in an integration gain of 30 dB. A good high-sensitivity GPS receiver can acquire signals down to −185 dBW, and tracking can be continued down to levels approaching −190 dBW. High-sensitivity GPS can provide positioning in many but not all indoor locations. Signals are either heavily attenuated by the building materials or reflected as in multipath. Given that high-sensitivity GPS receivers may be up to 30  dB more sensitive, this is sufficient to track through 3 layers of dry bricks, or up to 20 cm (8 inches) of steel-reinforced concrete, for example. Examples of high-sensitivity receiver chips include
SiRFstarIII SiRFstarIII is a range of high sensitivity GPS microcontroller chips manufactured by SiRF Technology. GPS microcontroller chips interpret signals from GPS satellites and determine the position of the GPS receiver. It was announced in 2004. Fe ...
and
MediaTek MediaTek Inc. () is a Taiwanese fabless semiconductor company that provides chips for wireless communications, high-definition television, handheld mobile devices like smartphones and tablet computers, navigation systems, consumer multimedia ...
ʼs MTK II.


Consumer applications

Consumer GNSS navigation devices include: * Dedicated GNSS navigation devices * modules that need to be connected to a computer to be used * loggers that record trip information for download. Such
GPS tracking A GPS tracking unit, geotracking unit, satellite tracking unit, or simply tracker is a navigation device normally on a vehicle, asset, person or animal that uses satellite navigation to determine its movement and determine its WGS84 UTM g ...
is useful for trailblazing, mapping by hikers and cyclists, and the production of geocoded photographs. * Converged devices, including Satnav phones and geotagging cameras, in which GNSS is a feature rather than the main purpose of the device. The majority of GNSS devices are now converged devices, and may use
assisted GPS 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 ...
or standalone (not network dependent) or both. The vulnerability of consumer GNSS to radio frequency interference from planned wireless data services is controversial.


Dedicated GNSS navigation devices

Dedicated devices have various degrees of mobility. ''Hand-held'', ''outdoor'', or ''sport'' receivers have replaceable batteries that can run them for several hours, making them suitable for
hiking Hiking is a long, vigorous walk, usually on trails or footpaths in the countryside. Walking for pleasure developed in Europe during the eighteenth century.AMATO, JOSEPH A. "Mind over Foot: Romantic Walking and Rambling." In ''On Foot: A Histor ...
,
bicycle touring Bicycle touring is the taking of self-contained cycling trips for pleasure, adventure or autonomy rather than sport, commuting or exercise. Bicycle touring can range from single-day trips to extended travels spanning weeks or months. Tours may be ...
and other activities far from an electric power source. Their design is ergonomical, their screens are small, and some do not show color, in part to save power. Some use transflective liquid-crystal displays, allowing use in bright sunlight. Cases are rugged and some are water-resistant. Other receivers, often called ''mobile'' are intended primarily for use in a car, but have a small rechargeable internal battery that can power them away from the car. Special purpose devices for use in a car may be permanently installed and depend entirely on the automotive electrical system. Many of them have touch-sensitive screens as input method. Maps may be stored on a
memory card A memory card is an electronic data storage device used for storing digital information, typically using flash memory. These are commonly used in digital portable electronic devices. They allow adding memory to such devices using a card in a so ...
. Some offer additional functionality such as a rudimentary music player,
image viewer An image viewer or image browser is a computer program that can display stored graphical images; it can often handle various graphics file formats. Such software usually renders the image according to properties of the display such as color depth, ...
, and
video player Media player software is a type of application software for playing multimedia computer files like audio and video files. Media players commonly display standard media control icons known from physical devices such as tape recorders and CD play ...
. The pre-installed embedded software of early receivers did not display maps; 21st-century ones commonly show interactive street maps (of certain regions) that may also show
points of interest A point of interest (POI) is a specific point location that someone may find useful or interesting. An example is a point on the Earth representing the location of the Eiffel Tower, or a point on Mars representing the location of its highest m ...
, route information and step-by-step routing directions, often in spoken form with a feature called "
text to speech Speech synthesis is the artificial production of human speech. A computer system used for this purpose is called a speech synthesizer, and can be implemented in software or hardware products. A text-to-speech (TTS) system converts normal languag ...
". Manufacturers include: * Navman products * TomTom products * Garmin products * Mio products * Navigon products * Magellan Navigation consumer products * Satmap Systems Ltd * TeleType products


Integration into smartphones

Almost all
smartphone A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...
s now incorporate GNSS receivers. This has been driven both by consumer demand and by service suppliers. There are now many phone apps that depend on location services, such as navigational aids, and multiple commercial opportunities, such as localised advertising. In its early development, access to user location services was driven by European and American emergency services to help locate callers. All smartphone operating systems offer free mapping and navigational services that require a data connection; some allow the pre-purchase and downloading of maps but the demand for this is diminishing as data connection reliant maps can generally be cached anyway. There are many navigation applications and new versions are constantly being introduced. Major apps include
Google Maps Navigation Google Maps Navigation is a mobile application developed by Google for the Android and iOS operating systems that was later integrated into the Google Maps mobile app. The application uses an Internet connection to a GPS navigation system to pro ...
, Apple Maps and
Waze Waze (; he, ווייז, label=Hebrew), formerly FreeMap Israel, is a subsidiary company of Google that provides satellite navigation software on smartphones and other computers that support the Global Positioning System (GPS). In addition to ...
, which require data connections, iGo for Android, Maverick and
HERE Here is an adverb that means "in, on, or at this place". It may also refer to: Software * Here Technologies, a mapping company * Here WeGo (formerly Here Maps), a mobile app and map website by Here Technologies, Here Television * Here TV (form ...
for Windows Phone, which use cached maps and can operate without a data connection. Consequently, almost any smartphone now qualifies as a
personal navigation assistant A Personal Navigation Assistant (PNA) also known as Personal Navigation Device or Portable Navigation Device (PND) is a portable electronic product which combines a positioning capability (such as GPS) and navigation functions. Some PNA devices a ...
. The use of mobile phones as navigational devices has outstripped the use of standalone GNSS devices. In 2009, independent analyst firm Berg Insight found that GNSS-enabled GSM/WCDMA handsets in the USA alone numbered 150 million units, against the sale of only 40 million standalone GNSS receivers.
Assisted GPS 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 ...
(A-GPS) uses a combination of satellite data and cell tower data to shorten the time to first fix, reduce the need to download a satellite almanac periodically and to help resolve a location when satellite signals are disturbed by the proximity of large buildings. When out of range of a cell tower the location performance of a phone using A-GPS may be reduced. Phones with an A-GPS based
hybrid positioning system A positioning system is a system for determining the position of an object in space. One of the most well-known and commonly used positioning systems is the Global Positioning System (GPS). Positioning system technologies exist ranging from worl ...
can maintain a location fix when GPS signals are inadequate by cell tower triangulation and WiFi hotspot locations. Most smartphones download a satellite almanac when online to accelerate a GPS fix when out of cell tower range. Some, older,
Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mos ...
-enabled phones lacking integrated GPS may still use external GPS receivers via serial or
Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limi ...
) connections, but the need for this is now rare. By
tethering Tethering, or phone-as-modem (PAM) is the sharing of a mobile device's Internet connection with other connected computers. Connection of a mobile device with other devices can be done over wireless LAN (Wi-Fi), over Bluetooth or by physical conne ...
to a laptop, some phones can provide localisation services to a laptop as well.


Palm, pocket and laptop PC

Software companies have made available
GPS navigation software Satellite navigation software or GPS navigation software usually falls into one of the following two categories: # Navigation with route calculation and directions from the software to the user of the route to take, based on a vector-based map, n ...
programs for in-vehicle use on laptop computers. Benefits of GPS on a laptop include larger map overview, ability to use the keyboard to control GPS functions, and some GPS software for laptops offers advanced trip-planning features not available on other platforms, such as midway stops, capability of finding alternative scenic routes as well as only highway option. Palms and Pocket PC's can also be equipped with GPS navigation. A pocket PC differs from a dedicated navigation device as it has an own operating system and can also run other applications.


GPS modules

Other GPS devices need to be connected to a computer in order to work. This computer can be a home computer, laptop, PDA,
digital camera A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile devices ...
, or
smartphone A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...
s. Depending on the type of computer and available connectors, connections can be made through a serial or
USB Universal Serial Bus (USB) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply (interfacing) between computers, peripherals and other computers. A broad ...
cable, as well as
Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limi ...
,
CompactFlash CompactFlash (CF) is a flash memory mass storage device used mainly in portable electronic devices. The format was specified and the devices were first manufactured by SanDisk in 1994. CompactFlash became one of the most successful of the e ...
, SD, PCMCIA and the newer ExpressCard. Some PCMCIA/ExpressCard GPS units also include a
wireless modem A mobile broadband modem, also known as wireless modem or cellular modem, is a type of modem that allows a personal computer or a router to receive wireless Internet access via a mobile broadband connection instead of using telephone or cable tel ...
. Devices usually do not come with pre-installed
GPS navigation software Satellite navigation software or GPS navigation software usually falls into one of the following two categories: # Navigation with route calculation and directions from the software to the user of the route to take, based on a vector-based map, n ...
, thus, once purchased, the user must install or write their own software. As the user can choose which software to use, it can be better matched to their personal taste. It is very common for a PC-based GPS receiver to come bundled with a navigation software suite. Also, software modules are significantly cheaper than complete stand-alone systems (around
The euro sign () is the currency sign used for the euro, the official currency of the eurozone and unilaterally adopted by Kosovo and Montenegro. The design was presented to the public by the European Commission on 12 December 1996. It consists ...
50 to €100). The software may include maps only for a particular region, or the entire world, if software such as Google Maps are used. Some hobbyists have also made some Satnav devices and open-sourced the plans. Examples include the Elektor GPS units. These are based around a
SiRFstarIII SiRFstarIII is a range of high sensitivity GPS microcontroller chips manufactured by SiRF Technology. GPS microcontroller chips interpret signals from GPS satellites and determine the position of the GPS receiver. It was announced in 2004. Fe ...
chip and are comparable to their commercial counterparts. Other chips and software implementations are also available.


Aviators

Aviators use Satnav to navigate and to improve safety and the efficiency of the flight. This may allow pilots to be independent of ground-based navigational aids, enable more efficient routes and provide navigation into airports that lack ground-based navigation and surveillance equipment. There are now some GPS units that allow aviators to get a clearer look in areas where the satellite is augmented to be able to have safe landings in bad visibility conditions. There have now been two new signals made for GPS, the first being made to help in critical conditions in the sky and the other will make GPS more of a robust navigation service. Many aviator services have now made it a required service to use a GPS. Commercial aviation applications include GNSS devices that calculate location and feed that information to large multi-input navigational computers for
autopilot An autopilot is a system used to control the path of an aircraft, marine craft or spacecraft without requiring constant manual control by a human operator. Autopilots do not replace human operators. Instead, the autopilot assists the operator' ...
, course information and correction displays to the pilots, and course tracking and recording devices.


Military

Military applications include devices similar to consumer sport products for foot soldiers (commanders and regular soldiers), small vehicles and ships, and devices similar to commercial aviation applications for aircraft and missiles. Examples are the United States military's Commander's Digital Assistant and the Soldier Digital Assistant. Prior to May 2000 only the military had access to the full accuracy of GPS. Consumer devices were restricted by
selective availability The error analysis for the Global Positioning System is important for understanding how GPS works, and for knowing what magnitude of error should be expected. The GPS makes corrections for receiver clock errors and other effects but there are sti ...
(SA), which was scheduled to be phased out but was removed abruptly by President Clinton.
Differential GPS 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 to . DGPSs c ...
is a method of cancelling out the error of SA and improving GPS accuracy, and has been routinely available in commercial applications such as for golf carts. GPS is limited to about 15 meter accuracy even without SA. DGPS can be within a few centimeters.


Sequential receivers

A sequential GPS receiver tracks the necessary satellites by typically using one or two hardware channels. The set will track one satellite at a time, time tag the measurements and combine them when all four satellite
pseudorange The pseudorange (from pseudo- and range) is the ''pseudo'' distance between a satellite and a navigation satellite receiver (see GNSS positioning calculation), for instance Global Positioning System (GPS) receivers. To determine its position ...
s have been measured. These receivers are among the least expensive available, but they cannot operate under high dynamics and have the slowest time-to-first-fix (TTFF) performance.


Hazards of relying on Satnav

GPS maps and directions are occasionally imprecise. Some people have gotten lost by asking for the shortest route, like a couple in the United States who were looking for the shortest route from South Oregon to
Jackpot, Nevada Jackpot is an unincorporated community and census-designated place (CDP) in Elko County, Nevada, United States. The population was 855 as of the 2020 census. Located less than from the Idaho border on US 93, Jackpot has been a popular casino g ...
. In August 2009 a young mother and her six-year-old son became stranded in
Death Valley Death Valley is a desert valley in Eastern California, in the northern Mojave Desert, bordering the Great Basin Desert. During summer, it is the Highest temperature recorded on Earth, hottest place on Earth. Death Valley's Badwater Basin is the ...
after following Satnav directions that led her up an unpaved dead-end road. When they were found five days later, her son had died from the effects of heat and
dehydration In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...
. In May 2012, Japanese tourists in Australia were stranded when traveling to
North Stradbroke Island North Stradbroke Island ( Jandai: ''Minjerribah''), colloquially ''Straddie'' or ''North Straddie'', is an island that lies within Moreton Bay in the Australian state of Queensland, southeast of the centre of Brisbane. Originally there was onl ...
and their satnav instructed them to drive into
Moreton Bay Moreton Bay is a bay located on the eastern coast of Australia from central Brisbane, Queensland. It is one of Queensland's most important coastal resources. The waters of Moreton Bay are a popular destination for recreational anglers and are ...
. In 2008 Satnav routed a softball team bus into a 9 ft tunnel, which sliced off the top of the bus and hospitalized the whole team. Brad Preston, Oregon claims that people are routed into his driveway five to eight times a week because their Satnav shows a street through his property. John and Starry Rhodes, a couple from Reno, Nevada were driving home from Oregon when they started to see there was a lot of snow in the area but decided to keep going because they were already 30 miles down the road. But the Satnav led them to a road in the Oregon forest that was not plowed and they were stuck for 3 days. Mary Davis was driving in an unfamiliar place when her Satnav told her to make a right turn onto a train track while there was a train coming down. Mary was lucky there was a local police officer who noticed the situation and urged her quickly to get out of the car as fast as she could. Mary was lucky enough to get out of the car leaving it for the train to hit and total it. The officer commented that there was a very good chance that they could have had a fatality on their hands. Other hazards involve an alley being listed as a street, a lane being identified as a road, or rail tracks as a road. Obsolete maps sometimes cause the unit to lead a user on an indirect, time-wasting route, because roads may change over time. Smartphone Satnav information is usually updated automatically, and free of additional charge. Manufacturers of separate Satnav devices also offer map update services for their merchandise, usually for a fee.


Privacy concerns

User privacy may be compromised if Satnav equipped handheld devices such as mobile phones upload user geo-location data through associated software installed on the device. User geo-location is currently the basis for navigational apps such as Google Maps,
location-based advertising Location-based advertising (LBA) is a form of advertising that integrates mobile advertising with location-based services. The technology is used to pinpoint consumers location and provide location-specific advertisements on their mobile devices. ...
, which can promote nearby shops and may allow an
advertising agency An advertising agency, often referred to as a creative agency or an ad agency, is a business dedicated to creating, planning, and handling advertising and sometimes other forms of promotion and marketing for its clients. An ad agency is generally ...
to track user movements and habits for future use. Regulatory bodies differ between countries regarding the treatment of geo-location data as privileged or not. Privileged data cannot be stored, or otherwise used, without the user's consent.
Vehicle tracking system A vehicle tracking system combines the use of automatic vehicle location in individual vehicles with software that collects these fleet data for a comprehensive picture of vehicle locations. Modern vehicle tracking systems commonly use GPS or G ...
s allow employers to track their employees' location raising questions regarding violation of employee privacy. There are cases where employers continued to collect geo-location data when an employee was off duty in private time.
Rental car Renting, also known as hiring or letting, is an agreement where a payment is made for the temporary use of a good, service or property owned by another. A gross lease is when the tenant pays a flat rental amount and the landlord pays for a ...
services may use the same technique to geo-fence their customers to the areas they have paid for, charging additional fees for violations. In 2010,
New York Civil Liberties Union The New York Civil Liberties Union (NYCLU) is a civil rights organization in the United States. Founded in November 1951 as the New York affiliate of the American Civil Liberties Union, it is a not-for-profit, nonpartisan organization with nea ...
filed a case against the Labor Department for firing Michael Cunningham after tracking his daily activity and locations using a Satnav device attached to his car.
Private investigator A private investigator (often abbreviated to PI and informally called a private eye), a private detective, or inquiry agent is a person who can be hired by individuals or groups to undertake investigatory law services. Private investigators of ...
s use planted GPS devices to provide information to their clients on a target's movements.


See also

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Comparison of web map services __TOC__ See also * GraphHopper * Navteq * Petal Maps * Online virtual globes * Tencent Maps * Traffic Message Channel (TMC) References {{Reflist External links Google MapsBing MapsMapQuest MapsMapy.czOpenStreetMapHereApple MapsYan ...
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Dashcam A dashboard camera or simply dashcam, also known as car digital video recorder (car DVR), driving recorder, or event data recorder (EDR), is an onboard camera that continuously records the view through a vehicle's front windscreen and sometimes ...
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Defense Advanced GPS Receiver The AN/PSN-13 Defense Advanced GPS Receiver (DAGR; colloquially, "dagger") is a handheld GPS receiver used by the United States Department of Defense and select foreign military services. It is a military-grade, dual-frequency receiver, and has t ...
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Head unit An automotive head unit, sometimes called the infotainment system, is a component providing a unified hardware interface for the system, including screens, buttons and system controls for numerous integrated information and entertainment func ...
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GPS watch A GPS watch is a device with integrated GPS receiver that is worn as a single unit strapped onto a wrist, in the manner of a bracelet. The watch can have other features and capabilities depending on its intended purpose and be a smartwatch. GPS w ...
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Precision Lightweight GPS Receiver The AN/PSN-11 Precision Lightweight GPS Receiver (PLGR, colloquially "plugger") is a ruggedized, hand-held, single-frequency GPS receiver fielded by the United States Armed Forces. It incorporates the Precise Positioning Service — Security ...
* Radio clock *
Turn-by-turn navigation Turn-by-turn Navigation is a feature of some satellite navigation devices where directions for a selected route are continually presented to the user in the form of spoken or visual instructions. The system keeps the user up-to-date about the best ...


References

{{Satellite navigation Global Positioning System Consumer electronics Navigational equipment device 20th-century inventions