global positioning system american satellite navigation system this article is about the american satellite navigation system it is not to be confused with similar nonamerican global and regional systems for similar systems see satellite navigation gps redirects here for the device see gps receiver for other uses see gps disambiguation global positioning system gps countryies of origin united states operator safs pc type military civilian status operational coverage global accuracy5 meters constellation size total satellites 33 satellites in orbit 31 first launch february 1978 40 years ago total launches 72 orbital characteristics regimes6x meo planesorbital height20180 km 12540 mi geodesy fundamentals geodesy geodynamics geomatics history concepts geographical distance geoid figure of the earth geodetic datum geodesic geographic coordinate system horizontal position representation latitude longitude map projection reference ellipsoid satellite geodesy spatial reference system spatial relations technologies global nav sat systems gnsss global pos system gps glonass russia beidou bds china galileo europe navic india quasizenith sat sys qzss japan discrete global grid and geocoding standards history ngvd 29 sea level datum 1929 osgb36 ordnance survey great britain 1936 sk42 systema koordinat 1942 goda ed50 european datum 1950 sad69 south american datum 1969 grs 80 geodetic reference system 1980 iso 6709 geographic point coord 1983 nad 83 north american datum 1983 wgs 84 world geodetic system 1984 navd 88 n american vertical datum 1988 etrs89 european terrestrial ref sys 1989 gcj02 chinese obfuscated datum 2002 geo uri internet link to a point 2010 international terrestrial reference system spatial reference system identifier srid universal transverse mercator utm vte media all and artists conception of gps block iif satellite in earth orbitcivilian gps receivers gps navigation device in a marine applicationautomotive navigation system in a taxicaba us air force senior airman runs through a checklist during global positioning system satellite operations the global positioning system gps originally navstar gps obstacles such as mountains and buildings block the relatively weak gps signals the gps does not require the user to transmit any data and it operates independently of any telephonic or internet reception though these technologies can enhance the usefulness of the gps positioning information the gps provides critical positioning capabilities to military civil and commercial users around the world the united states government created the system maintains it and makes it freely accessible to anyone with a gps receiver the gps project was launched by the us department of defense in 1973 for use by the united states military and became fully operational in 1995 it was allowed for civilian use in the 1980s advances in technology and new demands on the existing system have now led to efforts to modernize the gps and implement the next generation of gps block iiia satellites and next generation operational control system ocx the gps system is provided by the united states government which can selectively deny access to the system as happened to the indian military in 1999 during the kargil war or degrade the service at any time chinas beidou navigation satellite system is due to achieve global reach in 2020 there are also the european union galileo positioning system and indias navic japans quasizenith satellite system scheduled to commence in november 2018 will be a gps satellitebased augmentation system to enhance gpss accuracy when selective availability was lifted in 2000 gps had about 5 meter accuracy the latest stage of accuracy enhancement uses the l5 band and is now fully deployed gps receivers released in 2018 that use the l5 band can have much higher accuracy pinpointing to within 30 centimeters or just under one foot history air force film introducing the navstar global positioning system circa 1977 play media the gps project was launched in the united states in 1973 to overcome the limitations of previous navigation systems the design of gps is based partly on similar groundbased radionavigation systems such as loran and the decca navigator developed in the early 1940s predecessors when the soviet union launched the first artificial satellite sputnik 1 in 1957 two american physicists william guier and george weiffenbach at johns hopkins universitys applied physics laboratory apl decided to monitor its radio transmissions within hours they realized that because of the doppler effect they could pinpoint where the satellite was along its orbit the director of the apl gave them access to their univac to do the heavy calculations required early the next year frank mcclure the deputy director of the apl asked guier and weiffenbach to investigate the inverse problem pinpointing the users location given that of the satellite at the time the navy was developing the submarinelaunched polaris missile which required them to know the submarines location this led them and apl to develop the transit system transit was first successfully tested in 1960 it used a constellation of five satellites and could provide a navigational fix approximately once per hour in 1967 the us navy developed the timation satellite which proved the feasibility of placing accurate clocks in space a technology required for gps in the 1970s the groundbased omega navigation system based on phase comparison of signal transmission from pairs of stations became the first worldwide radio navigation system limitations of these systems drove the need for a more universal navigation solution with greater accuracy although there were wide needs for accurate navigation in military and civilian sectors almost none of those was seen as justification for the billions of dollars it would cost in research development deployment and operation of a constellation of navigation satellites during the cold war arms race the nuclear threat to the existence of the united states was the one need that did justify this cost in the view of the united states congress this deterrent effect is why gps was funded it is also the reason for the ultrasecrecy at that time the nuclear triad consisted of the united states navys submarinelaunched ballistic missiles slbms along with united states air force usaf strategic bombers and intercontinental ballistic missiles icbms considered vital to the nuclear deterrence posture accurate determination of the slbm launch position was a force multiplier precise navigation would enable united states ballistic missile submarines to get an accurate fix of their positions before they launched their slbms the usaf with two thirds of the nuclear triad also had requirements for a more accurate and reliable navigation system the navy and air force were developing their own technologies in parallel to solve what was essentially the same problem to increase the survivability of icbms there was a proposal to use mobile launch platforms comparable to the russian ss24 and ss25 and so the need to fix the launch position had similarity to the slbm situation in 1960 the air force proposed a radionavigation system called mosaic mobile system for accurate icbm control that was essentially a 3dloran a followon study project57 was worked in 1963 and it was in this study that the gps concept was born that same year the concept was pursued as project621b which had many of the attributes that you now see in gps and promised increased accuracy for air force bombers as well as icbms updates from the navy transit system were too slow for the high speeds of air force operation the naval research laboratory continued making advances with their timation time navigation satellites first launched in 1967 with the third one in 1974 carrying the first atomic clock into orbit another important predecessor to gps came from a different branch of the united states military in 1964 the united states army orbited its first sequential collation of range secor satellite used for geodetic surveying development with these parallel developments in the 1960s it was realized that a superior system could be developed by synthesizing the best technologies from 621b transit timation and secor in a multiservice program satellite orbital position errors induced by variations in the gravity field and radar refraction among others had to be resolved a team led by harold l jury of pan am aerospace division in florida from 19701973 used realtime data assimilation and recursive estimation to do so reducing systematic and residual errors to a manageable level to permit accurate navigation during labor day weekend in 1973 a meeting of about twelve military officers at the pentagon discussed the creation of a defense navigation satellite system dnss it was at this meeting that the real synthesis that became gps was created later that year the dnss program was named navstar or navigation system using timing and ranging the effects of the ionosphere on radio transmission through the ionosphere was investigated in a geophysics laboratory of air force cambridge research laboratory located at hanscom air force base outside boston the lab was renamed the air force geophysical research lab afgrl in 1974 afgrl developed the klobuchar model for computing ionospheric corrections to gps location after korean air lines flight 007 a boeing 747 carrying 269 people was shot down in 1983 after straying into the ussrs prohibited airspace initially the highestquality signal was reserved for military use and the signal available for civilian use was intentionally degraded in a policy known as selective availability this changed with president bill clinton signing on may 1 2000 a policy directive to turn off selective availability to provide the same accuracy to civilians that was afforded to the military the directive was proposed by the us secretary of defense william perry in view of the widespread growth of differential gps services to improve civilian accuracy and eliminate the us military advantage moreover the us military was actively developing technologies to deny gps service to potential adversaries on a regional basis since its deployment the us has implemented several improvements to the gps service including new signals for civil use and increased accuracy and integrity for all users all the while maintaining compatibility with existing gps equipment modernization of the satellite system has been an ongoing initiative by the us department of defense through a series of satellite acquisitions to meet the growing needs of the military civilians and the commercial market as of early 2015 highquality faa grade standard positioning service sps gps receivers provided horizontal accuracy of better than 35 meters although many factors such as receiver quality and atmospheric issues can affect this accuracy gps is owned and operated by the united states government as a national resource the department of defense is the steward of gps the interagency gps executive board igeb oversaw gps policy matters from 1996 to 2004 after that the national spacebased positioning navigation and timing executive committee was established by presidential directive in 2004 to advise and coordinate federal departments and agencies on matters concerning the gps and related systems the executive committee is chaired jointly by the deputy secretaries of defense and transportation its membership includes equivalentlevel officials from the departments of state commerce and homeland security the joint chiefs of staff and nasa components of the executive office of the president participate as observers to the executive committee and the fcc chairman participates as a liaison the us department of defense is required by law to maintain a standard positioning service as defined in the federal radio navigation plan and the standard positioning service signal specification that will be available on a continuous worldwide basis and develop measures to prevent hostile use of gps and its augmentations without unduly disrupting or degrading civilian uses timeline and modernization summary of satellites block launch period satellite launches currently in orbit and healthy success failure in preparation planned i 19781985 10 1 0 0 0 ii 19891990 9 0 0 0 0 iia 19901997 19 0 0 0 0 iir 19972004 12 1 0 0 12 iirm 20052009 8 0 0 0 7 iif 20102016 12 0 0 0 12 iiia from 2017 0 0 0 12 0 iiif 0 0 0 22 0 total 70 2 0 34 31 last update march 9 2016 8 satellites from block iia are placed in reserveusa203 from block iirm is unhealthy for a more complete list see list of gps satellite launches in 1972 the usaf central inertial guidance test facility holloman afb conducted developmental flight tests of four prototype gps receivers in a y configuration over white sands missile range using groundbased pseudosatellites in 1978 the first experimental blocki gps satellite was launched in 1983 after soviet interceptor aircraft shot down the civilian airliner kal 007 that strayed into prohibited airspace because of navigational errors killing all 269people on board us president ronald reagan announced that gps would be made available for civilian uses once it was completed and that the ca code coarseacquisition code would be available to civilian users by 1985 ten more experimental blocki satellites had been launched to validate the concept beginning in 1988 command and control of these satellites was moved from onizuka afs california to the 2nd satellite control squadron 2scs located at falcon air force station in colorado springs colorado on february 14 1989 the first modern blockii satellite was launched the gulf war from 1990 to 1991 was the first conflict in which the military widely used gps in 1991 a project to create a miniature gps receiver successfully ended replacing the previous 16 kg military receivers with a 125 kg handheld receiver in 1992 the 2nd space wing which originally managed the system was inactivated and replaced by the 50th space wing emblem of the 50th space wing by december 1993 gps achieved initial operational capability ioc with a full constellation 24 satellites available and providing the standard positioning service sps full operational capability foc was declared by air force space command afspc in april 1995 signifying full availability of the militarys secure precise positioning service pps in 1996 recognizing the importance of gps to civilian users as well as military users us president bill clinton issued a policy directive declaring gps a dualuse system and establishing an interagency gps executive board to manage it as a national asset in 1998 united states vice president al gore announced plans to upgrade gps with two new civilian signals for enhanced user accuracy and reliability particularly with respect to aviation safety and in 2000 the united states congress authorized the effort referring to it as gps iii on may 2 2000 selective availability was discontinued as a result of the 1996 executive order allowing civilian users to receive a nondegraded signal globally in 2004 the united states government signed an agreement with the european community establishing cooperation related to gps and europes galileo system in 2004 united states president george w bush updated the national policy and replaced the executive board with the national executive committee for spacebased positioning navigation and timing november 2004 qualcomm announced successful tests of assisted gps for mobile phones in 2005 the first modernized gps satellite was launched and began transmitting a second civilian signal l2c for enhanced user performance on september 14 2007 the aging mainframebased ground segment control system was transferred to the new architecture evolution plan on may 19 2009 the united states government accountability office issued a report warning that some gps satellites could fail as soon as 2010 on may 21 2009 the air force space command allayed fears of gps failure saying theres only a small risk we will not continue to exceed our performance standard on january 11 2010 an update of ground control systems caused a software incompatibility with 8000 to 10000 military receivers manufactured by a division of trimble navigation limited of sunnyvale calif on february 25 2010 the us air force awarded the contract to develop the gps next generation operational control system ocx to improve accuracy and availability of gps navigation signals and serve as a critical part of gps modernization awards on february 10 1993 the national aeronautic association selected the gps team as winners of the 1992 robert j collier trophy the nations most prestigious aviation award this team combines researchers from the naval research laboratory the usaf the aerospace corporation rockwell international corporation and ibm federal systems company the citation honors them for the most significant development for safe and efficient navigation and surveillance of air and spacecraft since the introduction of radio navigation 50years ago two gps developers received the national academy of engineering charles stark draper prize for 2003 ivan getting emeritus president of the aerospace corporation and an engineer at the massachusetts institute of technology established the basis for gps improving on the world war ii landbased radio system called loran longrange radio aid to navigation bradford parkinson professor of aeronautics and astronautics at stanford university conceived the present satellitebased system in the early 1960s and developed it in conjunction with the us air force parkinson served twentyone years in the air force from 1957 to 1978 and retired with the rank of colonel gps developer roger l easton received the national medal of technology on february 13 2006 francis x kane col usaf ret was inducted into the us air force space and missile pioneers hall of fame at lackland afb san antonio texas march 2 2010 for his role in space technology development and the engineering design concept of gps conducted as part of project 621b in 1998 gps technology was inducted into the space foundation space technology hall of fame on october 4 2011 the international astronautical federation iaf awarded the global positioning system gps its 60th anniversary award nominated by iaf member the american institute for aeronautics and astronautics aiaa the iaf honors and awards committee recognized the uniqueness of the gps program and the exemplary role it has played in building international collaboration for the benefit of humanity basic concept of gps fundamentals the gps concept is based on time and the known position of gps specialized satellites the satellites carry very stable atomic clocks that are synchronized with one another and with the ground clocks any drift from true time maintained on the ground is corrected daily in the same manner the satellite locations are known with great precision gps receivers have clocks as well but they are less stable and less precise gps satellites continuously transmit data about their current time and position a gps receiver monitors multiple satellites and solves equations to determine the precise position of the receiver and its deviation from true time at a minimum four satellites must be in view of the receiver for it to compute four unknown quantities three position coordinates and clock deviation from satellite time more detailed description each gps satellite continually broadcasts a signal carrier wave with modulation that includes a pseudorandom code sequence of ones and zeros that is known to the receiver by timealigning a receivergenerated version and the receivermeasured version of the code the time of arrival toa of a defined point in the code sequence called an epoch can be found in the receiver clock time scale a message that includes the time of transmission tot of the code epoch in gps time scale and the satellite position at that time conceptually the receiver measures the toas according to its own clock of four satellite signals from the toas and the tots the receiver forms four time of flight tof values which are given the speed of light approximately equivalent to receiversatellite ranges the receiver then computes its threedimensional position and clock deviation from the four tofs in practice the receiver position in three dimensional cartesian coordinates with origin at the earths center and the offset of the receiver clock relative to the gps time are computed simultaneously using the navigation equations to process the tofs the receivers earthcentered solution location is usually converted to latitude longitude and height relative to an ellipsoidal earth model the height may then be further converted to height relative to the geoid eg egm96 essentially mean sea level these coordinates may be displayed eg on a moving map display andor recorded andor used by some other system eg a vehicle guidance system usersatellite geometry although usually not formed explicitly in the receiver processing the conceptual time differences of arrival tdoas define the measurement geometry each tdoa corresponds to a hyperboloid of revolution see multilateration the line connecting the two satellites involved and its extensions forms the axis of the hyperboloid the receiver is located at the point where three hyperboloids intersect it is sometimes incorrectly said that the user location is at the intersection of three spheres while simpler to visualize this is the case only if the receiver has a clock synchronized with the satellite clocks ie the receiver measures true ranges to the satellites rather than range differences there are marked performance benefits to the user carrying a clock synchronized with the satellites foremost is that only three satellites are needed to compute a position solution if it were an essential part of the gps concept that all users needed to carry a synchronized clock a smaller number of satellites could be deployed but the cost and complexity of the user equipment would increase receiver in continuous operation the description above is representative of a receiver startup situation most receivers have a track algorithm sometimes called a tracker that combines sets of satellite measurements collected at different timesin effect taking advantage of the fact that successive receiver positions are usually close to each other after a set of measurements are processed the tracker predicts the receiver location corresponding to the next set of satellite measurements when the new measurements are collected the receiver uses a weighting scheme to combine the new measurements with the tracker prediction in general a tracker can a improve receiver position and time accuracy b reject bad measurements and c estimate receiver speed and direction the disadvantage of a tracker is that changes in speed or direction can be computed only with a delay and that derived direction becomes inaccurate when the distance traveled between two position measurements drops below or near the random error of position measurement gps units can use measurements of the doppler shift of the signals received to compute velocity accurately more advanced navigation systems use additional sensors like a compass or an inertial navigation system to complement gps nonnavigation applications for a list of applications see applications in typical gps operation as a navigator four or more satellites must be visible to obtain an accurate result the solution of the navigation equations gives the position of the receiver along with the difference between the time kept by the receivers onboard clock and the true timeofday thereby eliminating the need for a more precise and possibly impractical receiver based clock applications for gps such as time transfer traffic signal timing and synchronization of cell phone base stations make use of this cheap and highly accurate timing some gps applications use this time for display or other than for the basic position calculations do not use it at all although four satellites are required for normal operation fewer apply in special cases if one variable is already known a receiver can determine its position using only three satellites for example a ship or aircraft may have known elevation some gps receivers may use additional clues or assumptions such as reusing the last known altitude dead reckoning inertial navigation or including information from the vehicle computer to give a possibly degraded position when fewer than four satellites are visible structure this section needs additional citations for verification please help improve this article by adding citations to reliable sources unsourced material may be challenged and removed march 2015 learn how and when to remove this template message the current gps consists of three major segments these are the space segment a control segment and a user segment space segment see also gps satellite and list of gps satellites unlaunched gps block iia satellite on display at the san diego air space museum a visual example of a 24 satellite gps constellation in motion with the earth rotating notice how the number of satellites in view from a given point on the earths surface changes with time the point in this example is in golden colorado usa 397469 n 1052108 w the space segment ss is composed of 24 to 32 satellites in medium earth orbit and also includes the payload adapters to the boosters required to launch them into orbit the space segment ss is composed of the orbiting gps satellites or space vehicles sv in gps parlance the gps design originally called for 24svs eight each in three approximately circular orbits orbiting at an altitude of approximately 20200km 12600mi orbital radius of approximately 26600km 16500mi this was very helpful during development because even with only four satellites correct alignment means all four are visible from one spot for a few hours each day for military operations the ground track repeat can be used to ensure good coverage in combat zones as of february2016 about nine satellites are visible from any point on the ground at any one time see animation at right ensuring considerable redundancy over the minimum four satellites needed for a position control segment ground monitor station used from 1984 to 2007 on display at the air force space missile museum the control segment cs is composed of a master control station mcs an alternative master control station four dedicated ground antennas and six dedicated monitor stations the mcs can also access us air force satellite control network afscn ground antennas for additional command and control capability and nga national geospatialintelligence agency monitor stations the flight paths of the satellites are tracked by dedicated us air force monitoring stations in hawaii kwajalein atoll ascension island diego garcia colorado springs colorado and cape canaveral along with shared nga monitor stations operated in england argentina ecuador bahrain australia and washington dc satellite maneuvers are not precise by gps standardsso to change a satellites orbit the satellite must be marked unhealthy so receivers dont use it after the satellite maneuver engineers track the new orbit from the ground upload the new ephemeris and mark the satellite healthy again the operation control segment ocs currently serves as the control segment of record it provides the operational capability that supports gps users and keeps the gps operational and performing within specification ocs successfully replaced the legacy 1970sera mainframe computer at schriever air force base in september 2007 after installation the system helped enable upgrades and provide a foundation for a new security architecture that supported us armed forces ocs will continue to be the ground control system of record until the new segment next generation gps operation control system sustainment cost savings through efficient software architecture and performancebased logistics in addition gps ocx is expected to cost millions less than the cost to upgrade ocs while providing four times the capability the gps ocx program represents a critical part of gps modernization and provides significant information assurance improvements over the current gps ocs program ocx will have the ability to control and manage gps legacy satellites as well as the next generation of gps iii satellites while enabling the full array of military signals built on a flexible architecture that can rapidly adapt to the changing needs of todays and future gps users allowing immediate access to gps data and constellation status through secure accurate and reliable information provides the warfighter with more secure actionable and predictive information to enhance situational awareness enables new modernized signals l1c l2c and l5 and has mcode capability which the legacy system is unable to do provides significant information assurance improvements over the current program including detecting and preventing cyber attacks while isolating containing and operating during such attacks supports higher volume near realtime command and control capabilities and abilities on september 14 2011 the us air force announced the completion of gps ocx preliminary design review and confirmed that the ocx program is ready for the next phase of development the gps ocx program has missed major milestones and is pushing the gps iiia launch beyond april 2016 user segment further information gps navigation device gps receivers come in a variety of formats from devices integrated into cars phones and watches to dedicated devices such as these the first portable gps unit leica wm 101 displayed at the irish national science museum at maynooth the user segment us is composed of hundreds of thousands of us and allied military users of the secure gps precise positioning service and tens of millions of civil commercial and scientific users of the standard positioning service see gps navigation devices in general gps receivers are composed of an antenna tuned to the frequencies transmitted by the satellites receiverprocessors and a highly stable clock often a crystal oscillator they may also include a display for providing location and speed information to the user a receiver is often described by its number of channels this signifies how many satellites it can monitor simultaneously originally limited to four or five this has progressively increased over the years so that as of 2007 a typical oem gps receiver module measuring 1517mm gps receivers may include an input for differential corrections using the rtcm sc104 format this is typically in the form of an rs232 port at 4800bits speed data is actually sent at a much lower rate which limits the accuracy of the signal sent using rtcm even lowcost units commonly include wide area augmentation system waas receivers a typical gps receiver with integrated antenna many gps receivers can relay position data to a pc or other device using the nmea 0183 protocol although this protocol is officially defined by the national marine electronics association nmea other proprietary protocols exist as well such as the sirf and mtk protocols receivers can interface with other devices using methods including a serial connection usb or bluetooth applications this section needs additional citations for verification please help improve this article by adding citations to reliable sources unsourced material may be challenged and removed march 2015 learn how and when to remove this template message gnss applications see also gps navigation device while originally a military project gps is considered a dualuse technology meaning it has significant military and civilian applications gps has become a widely deployed and useful tool for commerce scientific uses tracking and surveillance gpss accurate time facilitates everyday activities such as banking mobile phone operations and even the control of power grids by allowing well synchronized handoff switching civilian this antenna is mounted on the roof of a hut containing a scientific experiment needing precise timing many civilian applications use one or more of gpss three basic components absolute location relative movement and time transfer astronomy both positional and clock synchronization data is used in astrometry and celestial mechanics gps is also used in both amateur astronomy with small telescopes as well as by professional observatories for finding extrasolar planets automated vehicle applying location and routes for cars and trucks to function without a human driver cartography both civilian and military cartographers use gps extensively cellular telephony clock synchronization enables time transfer which is critical for synchronizing its spreading codes with other base stations to facilitate intercell handoff and support hybrid gpscellular position detection for mobile emergency calls and other applications the first handsets with integrated gps launched in the late 1990s the us federal communications commission fcc mandated the feature in either the handset or in the towers for use in triangulation in 2002 so emergency services could locate 911callers thirdparty software developers later gained access to gps apis from nextel upon launch followed by sprint in 2006 and verizon soon thereafter clock synchronization the accuracy of gps time signals 10 ns is second only to the atomic clocks they are based on and is used in applications such as gps disciplined oscillators disaster reliefemergency services many emergency services depend upon gps for location and timing capabilities gpsequipped radiosondes and dropsondes measure and calculate the atmospheric pressure wind speed and direction up to 27km from the earths surface radio occultation for weather and atmospheric science applications fleet tracking used to identify locate and maintain contact reports with one or more fleet vehicles in realtime geofencing vehicle tracking systems person tracking systems and pet tracking systems use gps to locate devices that are attached to or carried by a person vehicle or pet the application can provide continuous tracking and send notifications if the target leaves a designated or fencedin area geotagging applies location coordinates to digital objects such as photographs in exif data and other documents for purposes such as creating map overlays with devices like nikon gp1 gps aircraft tracking gps for mining the use of rtk gps has significantly improved several mining operations such as drilling shoveling vehicle tracking and surveying rtk gps provides centimeterlevel positioning accuracy gps data mining it is possible to aggregate gps data from multiple users to understand movement patterns common trajectories and interesting locations gps tours location determines what content to display for instance information about an approaching point of interest navigation navigators value digitally precise velocity and orientation measurements phasor measurements gps enables highly accurate timestamping of power system measurements making it possible to compute phasors recreation for example geocaching geodashing gps drawing waymarking and other kinds of location based mobile games robotics selfnavigating autonomous robots using a gps sensors which calculate latitude longitude time speed and heading sport used in football and rugby for the control and analysis of the training load surveying surveyors use absolute locations to make maps and determine property boundaries tectonics gps enables direct fault motion measurement of earthquakes between earthquakes gps can be used to measure crustal motion and deformation to estimate seismic strain buildup for creating seismic hazard maps telematics gps technology integrated with computers and mobile communications technology in automotive navigation systems restrictions on civilian use the us government controls the export of some civilian receivers all gps receivers capable of functioning above 18km 60000 feet altitude and 515ms 1000 knots or designed or modified for use with unmanned air vehicles like eg ballistic or cruise missile systems are classified as munitions weaponswhich means they require state department export licenses this rule applies even to otherwise purely civilian units that only receive the l1 frequency and the ca coarseacquisition code disabling operation above these limits exempts the receiver from classification as a munition vendor interpretations differ the rule refers to operation at both the target altitude and speed but some receivers stop operating even when stationary this has caused problems with some amateur radio balloon launches that regularly reach 30km 100000 feet these limits only apply to units or components exported from the united states a growing trade in various components exists including gps units from other countries these are expressly sold as itarfree military attaching a gps guidance kit to a dumb bomb march 2003 m982 excalibur gpsguided artillery shell as of 2009 military gps applications include navigation soldiers use gps to find objectives even in the dark or in unfamiliar territory and to coordinate troop and supply movement in the united states armed forces commanders use the commanders digital assistant and lower ranks use the soldier digital assistant target tracking various military weapons systems use gps to track potential ground and air targets before flagging them as hostile these weapon systems pass target coordinates to precisionguided munitions to allow them to engage targets accurately military aircraft particularly in airtoground roles use gps to find targets missile and projectile guidance gps allows accurate targeting of various military weapons including icbms cruise missiles precisionguided munitions and artillery shells embedded gps receivers able to withstand accelerations of 12000 g or about 118kms2 have been developed for use in 155millimeter 61in howitzer shells search and rescue reconnaissance patrol movement can be managed more closely gps satellites carry a set of nuclear detonation detectors consisting of an optical sensor called a bhangmeter an xray sensor a dosimeter and an electromagnetic pulse emp sensor wsensor that form a major portion of the united states nuclear detonation detection system gps type navigation was first used in war in the 1991 persian gulf war before gps was fully developed in 1995 to assist coalition forces to navigate and perform maneuvers in the war the war also demonstrated the vulnerability of gps to being jammed when iraqi forces installed jamming devices on likely targets that emitted radio noise disrupting reception of the weak gps signal communication gps signals the navigational signals transmitted by gps satellites encode a variety of information including satellite positions the state of the internal clocks and the health of the network these signals are transmitted on two separate carrier frequencies that are common to all satellites in the network two different encodings are used a public encoding that enables lower resolution navigation and an encrypted encoding used by the us military message format gps message format subframes description 1 satellite clockgps time relationship 23 ephemerisprecise satellite orbit 45 almanac componentsatellite network synopsiserror correction each gps satellite continuously broadcasts a navigation message on l1 ca and py and l2 py frequencies at a rate of 50 bits per second see bitrate each complete message takes 750 seconds 12 12 minutes to complete the message structure has a basic format of a 1500bitlong frame made up of five subframes each subframe being 300 bits 6 seconds long subframes 4 and 5 are subcommutated 25 times each so that a complete data message requires the transmission of 25 full frames each subframe consists of ten words each 30 bits long thus with 300 bits in a subframe times 5 subframes in a frame times 25 frames in a message each message is 37500 bits long at a transmission rate of 50bits this gives 750 seconds to transmit an entire almanac message gps each 30second frame begins precisely on the minute or halfminute as indicated by the atomic clock on each satellite the first subframe of each frame encodes the week number and the time within the week all satellites broadcast at the same frequencies encoding signals using unique code division multiple access cdma so receivers can distinguish individual satellites from each other the system uses two distinct cdma encoding types the coarseacquisition ca code which is accessible by the general public and the precise py code which is encrypted so that only the us military and other nato nations who have been given access to the encryption code can access it the ephemeris is updated every 2 hours and is generally valid for 4 hours with provisions for updates every 6hours or longer in nonnominal conditions the almanac is updated typically every 24hours additionally data for a few weeks following is uploaded in case of transmission updates that delay data upload satellite frequencies gps frequency overview607 band frequency description l1 157542mhz coarseacquisition ca and encrypted precision py codes plus the l1 civilian l1c and military m codes on future block iii satellites l2 122760mhz py code plus the l2c and military codes on the block iirm and newer satellites l3 138105mhz used for nuclear detonation nudet detection l4 1379913mhz being studied for additional ionospheric correction l5 117645mhz proposed for use as a civilian safetyoflife sol signal all satellites broadcast at the same two frequencies 157542ghz l1 signal and 12276ghz l2signal the satellite network uses a cdma spreadspectrum technique the pcode can be encrypted as a socalled pycode that is only available to military equipment with a proper decryption key both the ca and pycodes impart the precise timeofday to the user the l3 signal at a frequency of 138105ghz is used to transmit data from the satellites to ground stations this data is used by the united states nuclear detonation nudet detection system usnds to detect locate and report nuclear detonations nudets in the earths atmosphere and near space one usage is the enforcement of nuclear test ban treaties the l4 band at 1379913ghz is being studied for additional ionospheric correction607 the l5 frequency band at 117645ghz was added in the process of gps modernization this frequency falls into an internationally protected range for aeronautical navigation promising little or no interference under all circumstances the first block iif satellite that provides this signal was launched in may 2010 in 2011 a conditional waiver was granted to lightsquared to operate a terrestrial broadband service near the l1 band although lightsquared had applied for a license to operate in the 1525 to 1559 band as early as 2003 and it was put out for public comment the fcc asked lightsquared to form a study group with the gps community to test gps receivers and identify issue that might arise due to the larger signal power from the lightsquared terrestrial network the gps community had not objected to the lightsquared formerly msv and skyterra applications until november 2010 when lightsquared applied for a modification to its ancillary terrestrial component atc authorization this filing satmod2010111800239 amounted to a request to run several orders of magnitude more power in the same frequency band for terrestrial base stations essentially repurposing what was supposed to be a quiet neighborhood for signals from space as the equivalent of a cellular network testing in the first half of 2011 has demonstrated that the impact of the lower 10mhz of spectrum is minimal to gps devices less than 1 of the total gps devices are affected the upper 10mhz intended for use by lightsquared may have some impact on gps devices there is some concern that this may seriously degrade the gps signal for many consumer uses demodulation and decoding demodulating and decoding gps satellite signals using the coarseacquisition gold code because all of the satellite signals are modulated onto the same l1 carrier frequency the signals must be separated after demodulation this is done by assigning each satellite a unique binary sequence known as a gold code the signals are decoded after demodulation using addition of the gold codes corresponding to the satellites monitored by the receiver if the almanac information has previously been acquired the receiver picks the satellites to listen for by their prns unique numbers in the range1 through 32 if the almanac information is not in memory the receiver enters a search mode until a lock is obtained on one of the satellites to obtain a lock it is necessary that there be an unobstructed line of sight from the receiver to the satellite the receiver can then acquire the almanac and determine the satellites it should listen for as it detects each satellites signal it identifies it by its distinct cacode pattern there can be a delay of up to 30seconds before the first estimate of position because of the need to read the ephemeris data processing of the navigation message enables the determination of the time of transmission and the satellite position at this time for more information see demodulation and decoding advanced navigation equations further information gnss positioning calculation see also pseudorange problem description the receiver uses messages received from satellites to determine the satellite positions and time sent the x y and z components of satellite position and the time sent are designated as where the subscript i denotes the satellite and has the value 1 2 n where n4 when the time of message reception indicated by the onboard receiver clock is ti the true reception time is ti ti b where b is the receivers clock bias from the much more accurate gps clocks employed by the satellites the receiver clock bias is the same for all received satellite signals assuming the satellite clocks are all perfectly synchronized the messages transit time is ti b si where si is the satellite time assuming the message traveled at the speed of light c the distance traveled is ti b si c for n satellites the equations to satisfy are d i t i b s i c i 1 2 n displaystyle dilefttilde tibsirightci12dots n where di is the geometric distance or range between receiver and satellite i the values without subscripts are the x y and z components of receiver position d i x x i 2 y y i 2 z z i 2 displaystyle disqrt xxi2yyi2zzi2 defining pseudoranges as p i t i s i c displaystyle pilefttilde tisirightc we see they are biased versions of the true range p i d i b c i 1 2 n displaystyle pidibci12n since the equations have four unknowns when n is greater than 4 this system is overdetermined and a fitting method must be used the amount of error in the results varies with the received satellites locations in the sky since certain configurations when the received satellites are close together in the sky cause larger errors receivers usually calculate a running estimate of the error in the calculated position this is done by multiplying the basic resolution of the receiver by quantities called the geometric dilution of position gdop factors calculated from the relative sky directions of the satellites used geometric interpretation the gps equations can be solved by numerical and analytical methods geometrical interpretations can enhance the understanding of these solution methods spheres the measured ranges called pseudoranges contain clock errors in a simplified idealization in which the ranges are synchronized these true ranges represent the radii of spheres each centered on one of the transmitting satellites the solution for the position of the receiver is then at the intersection of the surfaces of three of these spheres if more than the minimum number of ranges is available a near intersection of more than three sphere surfaces could be found via eg least squares hyperboloids if the pseudorange between the receiver and satellite i and the pseudorange between the receiver and satellite j are subtracted pi pj the common receiver clock bias b cancels out resulting in a difference of distances dj dj the locus of points having a constant difference in distance to two points here two satellites is a hyperbola on a plane and a hyperboloid of revolution in 3d space see multilateration thus from four pseudorange measurements the receiver can be placed at the intersection of the surfaces of three hyperboloids each with foci at a pair of satellites with additional satellites the multiple intersections are not necessarily unique and a bestfitting solution is sought instead inscribed sphere the receiver position can be interpreted as the center of a inscribed sphere insphere of radius bc given by the receiver clock bias b scaled by the speed of light c the insphere location is such that it touches other spheres see problem of apolloniusapplications the circumscribing spheres are centered at the gps satellites whose radii equal the measured pseudoranges pi this configuration is distinct from the one described in section spheres in which the spheres radii were the unbiased or geometric ranges di spherical cones the solution space with the cusp located at the satellite and the base a sphere around the satellite the receiver is at the intersection of four or more of such cones solution methods least squares when more than four satellites are available the calculation can use the four best or more than four simultaneously up to all visible satellites depending on the number of receiver channels processing capability and geometric dilution of precision gdop using more than four involves an overdetermined system of equations with no unique solution such a system can be solved by a leastsquares or weighted least squares method x y z b arg min x y z b i x x i 2 y y i 2 z z i 2 b c p i 2 displaystyle lefthat xhat yhat zhat brightunderset leftxyzbrightarg min sum ileftsqrt xxi2yyi2zzi2bcpiright2 iterative both the equations for four satellites or the least squares equations for more than four are nonlinear and need special solution methods a common approach is by iteration on a linearized form of the equations such as the gaussnewton algorithm the gps was initially developed assuming use of a numerical leastsquares solution methodie before closedform solutions were found closedform one closedform solution to the above set of equations was developed by s bancroft bancrofts method is algebraic as opposed to numerical and can be used for four or more satellites when four satellites are used the key steps are inversion of a 4x4 matrix and solution of a singlevariable quadratic equation bancrofts method provides one or two solutions for the unknown quantities when there are two usually the case only one is a nearearth sensible solution when a receiver uses more than four satellites for a solution bancroft uses the generalized inverse ie the pseudoinverse to find a solution a case has been made that iterative methods eg gaussnewton algorithm for solving overdetermined nonlinear least squares nlls problems generally provide more accurate solutions leick et al 2015 states that bancrofts 1985 solution is a very early if not the first closedform solution other closedform solutions were published afterwards although their adoption in practice is unclear error sources and analysis error analysis for the global positioning system gps error analysis examines error sources in gps results and the expected size of those errors gps makes corrections for receiver clock errors and other effects but some residual errors remain uncorrected error sources include signal arrival time measurements numerical calculations atmospheric effects ionospherictropospheric delays ephemeris and clock data multipath signals and natural and artificial interference magnitude of residual errors from these sources depends on geometric dilution of precision artificial errors may result from jamming devices and threaten ships and aircraft accuracy enhancement and surveying gnss enhancement this article duplicates the scope of other articles specifically gnss enhancement please discuss this issue on the talk page and edit it to conform with wikipedias manual of style november 2013 augmentation integrating external information into the calculation process can materially improve accuracy such augmentation systems are generally named or described based on how the information arrives some systems transmit additional error information such as clock drift ephemera or ionospheric delay others characterize prior errors while a third group provides additional navigational or vehicle information examples of augmentation systems include the wide area augmentation system waas european geostationary navigation overlay service egnos differential gps dgps inertial navigation systems ins and assisted gps the standard accuracy of about 15 meters 49 feet can be augmented to 35 meters 98164ft with dgps and to about 3 meters 98 feet with waas precise monitoring accuracy can be improved through precise monitoring and measurement of existing gps signals in additional or alternative ways the largest remaining error is usually the unpredictable delay through the ionosphere the spacecraft broadcast ionospheric model parameters but some errors remain this is one reason gps spacecraft transmit on at least two frequencies l1 and l2 ionospheric delay is a welldefined function of frequency and the total electron content tec along the path so measuring the arrival time difference between the frequencies determines tec and thus the precise ionospheric delay at each frequency military receivers can decode the py code transmitted on both l1 and l2 without decryption keys it is still possible to use a codeless technique to compare the py codes on l1 and l2 to gain much of the same error information this technique is slow so it is currently available only on specialized surveying equipment in the future additional civilian codes are expected to be transmitted on the l2 and l5frequencies see gps modernization all users will then be able to perform dualfrequency measurements and directly compute ionospheric delay errors a second form of precise monitoring is called carrierphase enhancement cpgps this corrects the error that arises because the pulse transition of the prn is not instantaneous and thus the correlation satellitereceiver sequence matching operation is imperfect cpgps uses the l1 carrier wave which has a period of 1 s 157542 10 6 063475 n s 1 n s displaystyle frac 1mathrm s 157542times 106063475mathrm ns approx 1mathrm ns which is about onethousandth of the cagold code bit period of 1 s 1023 10 3 9775 n s 1000 n s displaystyle frac 1mathrm s 1023times 1039775mathrm ns approx 1000mathrm ns to act as an additional clock signal and resolve the uncertainty the phase difference error in the normal gps amounts to 23 meters 710ft of ambiguity cpgps working to within 1 of perfect transition reduces this error to 3 centimeters 12in of ambiguity by eliminating this error source cpgps coupled with dgps normally realizes between 2030 centimeters 812in of absolute accuracy relative kinematic positioning rkp is a third alternative for a precise gpsbased positioning system in this approach determination of range signal can be resolved to a precision of less than 10 centimeters 4in this is done by resolving the number of cycles that the signal is transmitted and received by the receiver by using a combination of differential gps dgps correction data transmitting gps signal phase information and ambiguity resolution techniques via statistical testspossibly with processing in realtime realtime kinematic positioning rtk timekeeping leap seconds while most clocks derive their time from coordinated universal time utc the atomic clocks on the satellites are set to gps time gpst see the page of united states naval observatory the difference is that gps time is not corrected to match the rotation of the earth so it does not contain leap seconds or other corrections that are periodically added to utc gps time was set to match utc in 1980 but has since diverged the lack of corrections means that gps time remains at a constant offset with international atomic time tai tai gps 19seconds periodic corrections are performed to the onboard clocks to keep them synchronized with ground clocks the gps navigation message includes the difference between gps time and utc as of january2017 receivers subtract this offset from gps time to calculate utc and specific timezone values new gps units may not show the correct utc time until after receiving the utc offset message the gpsutc offset field can accommodate 255 leap seconds eight bits accuracy gps time is theoretically accurate to about 14 nanoseconds due to the clock drift that atomic clocks experience in gps transmittersper or relative to what format as opposed to the year month and day format of the gregorian calendar the gps date is expressed as a week number and a secondsintoweek number the week number is transmitted as a tenbit field in the ca and py navigation messages and so it becomes zero again every 1024weeks 196years gps week zero started at 000000utc 000019tai on january 6 1980 and the week number became zero again for the first time at 235947utc on august 21 1999 000019tai on august 22 1999 to determine the current gregorian date a gps receiver must be provided with the approximate date to within 3584days to correctly translate the gps date signal to address this concern the modernized gps navigation message uses a 13bit field that only repeats every 8192weeks 157years thus lasting until 2137 157years after gps week zero carrier phase tracking surveying another method that is used in surveying applications is carrier phase tracking the period of the carrier frequency multiplied by the speed of light gives the wavelength which is about 019meters for the l1carrier accuracy within 1 of wavelength in detecting the leading edge reduces this component of pseudorange error to as little as 2millimeters this compares to 3meters for the ca code and 03meters for the pcode 2millimeter accuracy requires measuring the total phasethe number of waves multiplied by the wavelength plus the fractional wavelength which requires specially equipped receivers this method has many surveying applications it is accurate enough for realtime tracking of the very slow motions of tectonic plates typically 0100mm 04 inches per year triple differencing followed by numerical root finding and a mathematical technique called least squares can estimate the position of one receiver given the position of another first compute the difference between satellites then between receivers and finally between epochs other orders of taking differences are equally valid detailed discussion of the errors is omitted the satellite carrier total phase can be measured with ambiguity as to the number of cycles let r i s j t k displaystyle phi risjtk denote the phase of the carrier of satellite j measured by receiver i at time t k displaystyle tk this notation shows the meaning of the subscripts i j and k the receiver r satellite s and time t come in alphabetical order as arguments of displaystyle phi and to balance readability and conciseness let i j k r i s j t k displaystyle phi ijkphi risjtk be a concise abbreviation also we define three functions r s t displaystyle delta rdelta sdelta t which return differences between receivers satellites and time points respectively each function has variables with three subscripts as its arguments these three functions are defined below if i j k displaystyle alpha ijk is a function of the three integer arguments i j and k then it is a valid argument for the functions r s t displaystyle delta rdelta sdelta t with the values defined as r i j k i 1 j k i j k displaystyle delta ralpha ijkalpha i1jkalpha ijk s i j k i j 1 k i j k displaystyle delta salpha ijkalpha ij1kalpha ijk and t i j k i j k 1 i j k displaystyle delta talpha ijkalpha ijk1alpha ijk also if i j k a n d l m n displaystyle alpha ijk and beta lmn are valid arguments for the three functions and a and b are constants then a i j k b l m n displaystyle a alpha ijkb beta lmn is a valid argument with values defined as r a i j k b l m n a r i j k b r l m n displaystyle delta ra alpha ijkb beta lmna delta ralpha ijkb delta rbeta lmn s a i j k b l m n a s i j k b s l m n displaystyle delta sa alpha ijkb beta lmna delta salpha ijkb delta sbeta lmn and t a i j k b l m n a t i j k b t l m n displaystyle delta ta alpha ijkb beta lmna delta talpha ijkb delta tbeta lmn receiver clock errors can be approximately eliminated by differencing the phases measured from satellite1 with that from satellite2 at the same epoch this difference is designated as s 1 1 1 1 2 1 1 1 1 displaystyle delta sphi 111phi 121phi 111 double differencing computes the difference of receiver1s satellite difference from that of receiver2 this approximately eliminates satellite clock errors this double difference is r s 1 1 1 r 1 2 1 1 1 1 r 1 2 1 r 1 1 1 2 2 1 1 2 1 2 1 1 1 1 1 displaystyle beginaligneddelta rdelta sphi 111delta rphi 121phi 111delta rphi 121delta rphi 111phi 221phi 121phi 211phi 111endaligned triple differencing subtracts the receiver difference from time1 from that of time2 this eliminates the ambiguity associated with the integral number of wavelengths in carrier phase provided this ambiguity does not change with time thus the triple difference result eliminates practically all clock bias errors and the integer ambiguity atmospheric delay and satellite ephemeris errors have been significantly reduced this triple difference is t r s 1 1 1 displaystyle delta tdelta rdelta sphi 111 triple difference results can be used to estimate unknown variables for example if the position of receiver1 is known but the position of receiver2 unknown it may be possible to estimate the position of receiver2 using numerical root finding and least squares triple difference results for three independent time pairs may be sufficient to solve for receiver2s three position components this may require a numerical procedure an approximation of receiver2s position is required to use such a numerical method this initial value can probably be provided from the navigation message and the intersection of sphere surfaces such a reasonable estimate can be key to successful multidimensional root finding iterating from three time pairs and a fairly good initial value produces one observed triple difference result for receiver2s position processing additional time pairs can improve accuracy overdetermining the answer with multiple solutions least squares can estimate an overdetermined system least squares determines the position of receiver2 that best fits the observed triple difference results for receiver2 positions under the criterion of minimizing the sum of the squares regulatory spectrum issues concerning gps receivers in the united states gps receivers are regulated under the federal communications commissions fcc part 15 rules as indicated in the manuals of gpsenabled devices sold in the united states as a part 15 device it must accept any interference received including interference that may cause undesired operation for the last 30 years gps receivers have operated next to the mobile satellite service band and have discriminated against reception of mobile satellite services such as inmarsat without any issue the spectrum allocated for gps l1 use by the fcc is 1559 to 1610mhz while the spectrum allocated for satellitetoground use owned by lightsquared is the mobile satellite service band in january 2011 the fcc conditionally authorized lightsquareds wholesale customerssuch as best buy sharp and c spireto only purchase an integrated satellitegroundbased service from lightsquared and resell that integrated service on devices that are equipped to only use the groundbased signal using lightsquareds allocated frequencies of 1525 to 1559mhz although the fccs policy considerations leading up to the january 2011 order did not pertain to any proposed changes to the maximum number of groundbased lightsquared stations or the maximum power at which these stations could operate the january 2011 order makes final authorization contingent upon studies of gps interference issues carried out by a lightsquared led working group along with gps industry and federal agency participation on february 14 2012 the fcc initiated proceedings to vacate lightsquareds conditional waiver order based on the ntias conclusion that there was currently no practical way to mitigate potential gps interference gps receiver manufacturers design gps receivers to use spectrum beyond the gpsallocated band in some cases gps receivers are designed to use up to 400mhz of spectrum in either direction of the l1 frequency of 157542mhz because mobile satellite services in those regions are broadcasting from space to ground and at power levels commensurate with mobile satellite services this is why gps operates next to the mobile satellite service band and also why the mobile satellite service band operates next to gps the symbiotic relationship of spectrum allocation ensures that users of both bands are able to operate cooperatively and freely the fcc adopted rules in february 2003 that allowed mobile satellite service mss licensees such as lightsquared to construct a small number of ancillary groundbased towers in their licensed spectrum to promote more efficient use of terrestrial wireless spectrum the fcc and lightsquared have each made public commitments to solve the gps interference issue before the network is allowed to operate on february 14 2012 the us federal communications commission fcc moved to bar lightsquareds planned national broadband network after being informed by the national telecommunications and information administration ntia the federal agency that coordinates spectrum uses for the military and other federal government entities that there is no practical way to mitigate potential interference at this time lightsquared is challenging the fccs action other systems satellite navigation comparison of geostationary gps glonass galileo compass meo international space station hubble space telescope iridium constellation and graveyard orbits with the van allen radiation belts and the earth to scale in thesvgfile hover over an orbit or its label to highlight it click to load its article other satellite navigation systems in use or various states of development include glonass russias global navigation system fully operational worldwide galileo a global system being developed by the european union and other partner countries which began operation in 2016 and is expected to be fully deployed by 2020 beidou peoples republic of chinas regional system currently limited to asia and the west pacific irnss a regional navigation system developed by the indian space research organisation qzss a regional navigation system in development that would be receivable within japan gladys west gpsins gps navigation software gps navigation device gps spoofing indoor positioning system list of gps satellites local area augmentation system local positioning system military invention mobile phone tracking navigation paradox notice advisory to navstar users sgps trilateration wide area augmentation system notes navstar gps user equipment introduction pdf united states coast guard september 1996 parkinson spilker 1996 the global positioning system american institute of aeronautics and astronautics isbn9781563471063 jaizki mendizabal roc berenguer juan melendez 2009 gps and galileo mcgraw hill isbn9780071598699 nathaniel bowditch 2002 the american practical navigator chapter 11 satellite navigation united states government global positioning system open courseware from mit 2012 wikimedia commons has media related to global positioning system global positioning system at curlie faa gps faq gpsgovgeneral public education website created by the us government us army corps of engineers manualnavstar html archived from the original on august 22 2008 retrieved 20100606cs1 maint bot originalurl status unknown link andpdf 226 mb 328 pages pdf archived from the original on june 25 2008 retrieved 20100606cs1 maint bot originalurl status unknown link national geodetic survey orbits for the global positioning system satellites in the global navigation satellite system gps and glonass simulation java applet simulation and graphical depiction of space vehicle motion including computation of dilution of precision dop relativity science calculator explaining global positioning system vtenavstar global positioning system satelliteslist of gps satellitesblock i 1 2 3 4 5 6 7 8 9 10 11 block ii 1 2 3 4 5 6 7 8 9 block iia 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 block iir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 block iirm 1 2 3 4 5 6 7 8 block iif 1 2 3 4 5 6 7 8 9 10 11 12 block iiia 1 2 3 4 5 6 7 8 9 10 block iiif 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 italics indicate future missions signs indicate launch failures vtesatellite navigation systemsoperational bds beidou2 compass doris galileo glonass gps navstar irnss navic historical bds beidou1 transit timation tsiklon gnss augmentation egnos gagan gpsc retired jpals laas msas ntrip qzss michibiki starfire waas related topics gnss reflectometry kalman filter wavelet vtetime signal stationslongwave bpc bpl bsf dcf77 jjy rbu rjh beta rns chayka rtz msf tdf wwvb shortwave bpm chu ebc hd2ioa hla jn53dv lol rwm wwv wwvh hawaii usa yvto vhffmuhf rds ct satellite gps beidou galileo glonass irnss qzss defunct ata bsf shortwave hbg naa wwvl oma olb5 vng y3s vtesystems sciencesystems types anatomical art biological complex complex adaptive conceptual coupled humanenvironment database dynamical ecological economic energy formal holarchic information legal measurement metric multiagent nervous nonlinear operating physical planetary political sensory social star writing concepts doubling time leverage points limiting factor negative feedback positive feedback theoretical fields chaos theory complex systems control theory cybernetics earth system science living systems sociotechnical system systemics urban metabolism worldsystems theory analysis biology dynamics ecology engineering neuroscience pharmacology psychology theory thinking systems scientists alexander bogdanov russell l ackoff william ross ashby ruzena bajcsy bla h bnthy gregory bateson anthony stafford beer richard e bellman ludwig von bertalanffy margaret boden kenneth e boulding murray bowen kathleen carley mary cartwright c west churchman manfred clynes george dantzig edsger w dijkstra heinz von foerster stephanie forrest jay wright forrester barbara grosz charles a s hall lydia kavraki james j kay faina m kirillova george klir allenna leonard edward norton lorenz niklas luhmann humberto maturana margaret mead donella meadows mihajlo d mesarovic james grier miller radhika nagpal howard t odum talcott parsons ilya prigogine qian xuesen anatol rapoport peter senge claude shannon katia sycara francisco varela manuela m veloso kevin warwick norbert wiener jennifer wilby anthony wilden applications systems theory in anthropology systems theory in archaeology systems theory in political science organizations list principia cybernetica category portal commons vteflight instrumentspitotstatic altimeter airspeed indicator machmeter variometer gyroscopic attitude indicator heading indicator horizontal situation indicator turn and slip indicator turn coordinator turn indicator navigational course deviation indicator horizontal situation indicator inertial navigation system magnetic compass satellite navigation sigi related topics air data inertial reference unit ecam efis glass cockpit primary flight display v speeds yaw string vteautomotive designpart of a series of articles on carsbodyframework backbone chassis beltline bodyonframe bumper cabrio coach chassis continental tire crumple zone dagmar bumpers fender fender skirts grille hood hood scoop monocoque overhang pillar platform pontoon fenders quarter panel roof rack shaker scoop spoiler stressed member engine subframe tonneau trunk lid compartments trunkbootdickie hoodbonnet doors butterfly canopy gullwing scissor sliding suicide glass greenhouse power window quarter glass opera window sunroof windshieldwindscreen windshieldwindscreen wiper other elements bumper sticker curb feeler frontend bra hood ornament japan black nerf bar omniview technology runflat tire spare tire tiretyre tow hitch truck accessory window deflector geometry approach and departure angles breakover angle overhang ride height roll center turning radius weight distribution exteriorequipmentlighting daytime running lamp headlamp sealed beam highintensity discharge lamp hidden headlamps turn signals trafficators rear position lamps stop lamps reversing lamps safety reflector retroreflector other elements horn registration plate vanity plate windshieldwindscreen washer fluid wing mirror power sideview mirror legal identification number theft category commons portal vte1962present united states air force space vehicle designationsslv series slv1 slv2 slv3 slv4 slv5 sb series sb1 sb2 sb3 sb4 sb5 sb6 ssb7 ssb8 ssb9 ssb10 asb11 satellites ws1 ws2 ls3 es4 es5 ls6 ns7 es8 ls9 ls10 i xss10 ii xss112 xss12 s131 es14 ls153 ls163 es17 1 not assigned 2 unofficial designation 3 designation believed to be this type but unconfirmed vteequipment of the united states air forceactive service aircraft designationa attack aoa10ac thunderbolt ii ac130hujw spectrespooky iighostriderstinger ii b strategic bomber b1b lancer b2a spirit b52h stratofortress c cargo transport c5c galaxy c5m super galaxy c12cdf huron c17a globemaster iii c20b gulfstream iii c20h gulfstream iv c21a learjet c27j spartan c37a gulfstream v c40bc clipper c130ehjj30 hercules cv22b osprey e special electronic e3bc sentry e4b e8c joint stars e9a widget e11a bacn ec130h compass call ec130j commando solo f fighter f15cd eagle f15e strike eagle f16cd fighting falcon f22a raptor f35a lightning ii h search and rescue hc130pn king hc130j combat king ii hh60gmh60g pave hawk k tanker kc10a extender kc135ert stratotanker l cold weather lc130h m multimission cv22 osprey mc130ehjp combat talon icombat talon iicommando iicombat shadow mc12w liberty o observation oc135b open skies q remotely piloted mq9 reaper rq4a global hawk rq11b raven rq170 sentinel rq180 r reconnaissance rc26b condor rc135suvw cobra ballcombat sentrivet joint scan eagle ru2s dragon lady wasp iii t trainer t1a jayhawk t6a texan ii at38abc talon ii tg10bcd tg15ab diamond t52a u utility uh1n iroquois uh1hnv huey uv18ab twin otter u28a v vipstaff transport vc9c vc25a air force one c32ab air force two c40bc clipper w weather reconnaissance wc130j hercules wc135w constant phoenix otherundesignated an26 6th sos cn235100 427th sos mi8 6th sos spacesystemslaunch vehicle atlas v delta iv satellite advanced extremely high frequency aehf defense meteorological satellite program dmsp defense satellite communications system dscs defense support program dsp global positioning system gps milstar satellite communications system spacebased infrared system sbirs wideband global satcom groundsystemsc2 anusq163 falconer angsq272 sentinel groundbasedradar anfpq16 perimeter acquisition attack characterization system parcs anfps123 early warning radar ewr anfps132 upgraded early warning radar uewr anfps85 anfps133 air force space surveillance system afsss anfsq114 groundbased electrooptical deep space surveillance geodss anfsq224 morn optical space surveillance moss rapid attack identification detection and reporting system raidrs ground vehicle hmmwv lssv r5 refueler r9 refueler r11 refueler c300 munitionsbomb mk82 mk84 gbu8 gbu10 paveway ii gbu12 paveway ii gbu15 gbu24 paveway iii gbu27 paveway iii gbu28 gbu31 jdam gbu32 jdam gbu38 jdam gbu39 small diameter bomb gbu44b viper strike gbu53b small diameter bomb ii gbu54 laser jdam cbu87 combined effects munition cbu89 gator cbu97 sensor fuzed weapon blu109b bomb blu116 bunker buster b61 nuclear bomb b83 nuclear bomb gun gau8 avenger m61 vulcan gau12 gau13 gau19 m240 l60 bofors m102 atk gau23a m2 browning minigun missile aim7m sparrow aim9mx sidewinder lgm30g minuteman iii agm65abdegg2hk maverick agm84 harpoon agm84e standoff land attack missile agm84hk standoff land attack missile expanded response agm86bcd airlaunched cruise missile alcm agm88abc highspeed antiradiation missile harm agm114 hellfire airtosurface missile asm aim120bc advanced mediumrange airtoair missile amraam agm130 powered standoff weapon agm154a joint standoff weapon jsow agm158 joint airtosurface standoff missile jassm agm176 griffin zuni rocket target bqm34 firebee bqm167 subscale aerial target mqm107 streaker qf4 aerial target small armssidearmpdw m11 pistol m9 pistol m17 pistol mp5 submachine gun usaf pilots survival knife riflecarbine guu5p carbine m4 carbine m14 standoff munitions disruptor smud m16a2 rifle m24 sniper weapon system m107 long range sniper rifle mk 14 mod 0 enhanced battle rifle supportcqb m60 machine gun m2hb browning machine gun m240b medium machine gun m249 light machine gun m1014 shotgun remington 870 mcs shotgun ordnance m136 at4 light antitank weapon m18a1 claymore mine m67 fragmentation grenade m72 light antitank weapon law m79 grenade launcher mk19 automatic grenade launcher uniforms other equipment airman battle uniform abu airman combat uniform acu flight suit physical training uniform service dress uniform mess dress cmu 33ap22p18 vteorienteering history of orienteering list of orienteering events sport disciplinesiofgoverned foot orienteering mountain bike orienteering ski orienteering trail orienteering iarugoverned amateur radio direction finding fox oring radio orienteering in a compact area other sports canoe orienteering car orienteering mountain marathon mounted orienteering rogaining related adventure racing alleycat race fell running relay race transmitter hunting equipmentevent control point course map personal compass hand protractor thumb eye protectors gaiters headlamp exceptions backpacking gps whistle fundamentals map orienteering map navigation cardinal direction resection route choice wayfinding waypoint racing hiking running walking skiing mountain biking organisations lists international orienteering federation members list of clubs list of orienteers by 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