Global Positioning System

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stated: "As a preliminary matter, terrestrial and MSS ATC are expected to have different prices, coverage, product acceptance and distribution; therefore, the two services appear, at best, to be imperfect substitutes for one another that would be operating in predominantly different market segments ... MSS ATC is unlikely to compete directly with terrestrial CMRS for the same customer base...". In 2004, the FCC clarified that the ground-based towers would be ancillary, noting: "We will authorize MSS ATC subject to conditions that ensure that the added terrestrial component remains ancillary to the principal MSS offering. We do not intend, nor will we permit, the terrestrial component to become a stand-alone service." In July 2010, the FCC stated that it expected LightSquared to use its authority to offer an integrated satellite-terrestrial service to "provide mobile broadband services similar to those provided by terrestrial mobile providers and enhance competition in the mobile broadband sector". GPS receiver manufacturers have argued that LightSquared's licensed spectrum of 1525 to 1559 MHz was never envisioned as being used for high-speed wireless broadband based on the 2003 and 2004 FCC ATC rulings making clear that the Ancillary Tower Component (ATC) would be, in fact, ancillary to the primary satellite component. To build public support of efforts to continue the 2004 FCC authorization of LightSquared's ancillary terrestrial component vs. a simple ground-based LTE service in the Mobile Satellite Service band, GPS receiver manufacturer

3219: 5306:—to only purchase an integrated satellite-ground-based service from LightSquared and re-sell that integrated service on devices that are equipped to only use the ground-based signal using LightSquared's allocated frequencies of 1525 to 1559 MHz. In December 2010, GPS receiver manufacturers expressed concerns to the FCC that LightSquared's signal would interfere with GPS receiver devices although the FCC's policy considerations leading up to the January 2011 order did not pertain to any proposed changes to the maximum number of ground-based 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 LightSquared's Conditional Waiver Order based on the NTIA's conclusion that there was currently no practical way to mitigate potential GPS interference. 3784:

identify issues 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 (SAT-MOD-20101118-00239) 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 10 MHz of spectrum is minimal to GPS devices (less than 1% of the total GPS devices are affected). The upper 10 MHz 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.

2459:, 27 of which are in use at a given time with the rest allocated as stand-bys. A 32nd was launched in 2018, but as of July 2019 is still in evaluation. More decommissioned satellites are in orbit and available as spares. The additional satellites improve the precision of GPS receiver calculations by providing redundant measurements. With the increased number of satellites, the constellation was changed to a nonuniform arrangement. Such an arrangement was shown to improve accuracy but also improves reliability and availability of the system, relative to a uniform system, when multiple satellites fail. With the expanded constellation, nine satellites are usually visible at any time from any point on the Earth with a clear horizon, ensuring considerable redundancy over the minimum four satellites needed for a position. 2637: 5363: 310: 3740:. 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. On February 5, 2016, the 12th and final Block IIF satellite was launched. The L5 consists of two carrier components that are in phase quadrature with each other. Each carrier component is bi-phase shift key (BPSK) modulated by a separate bit train. "L5, the third civil GPS signal, will eventually support safety-of-life applications for aviation and provide improved availability and accuracy." 1848: 2184:, that combines sets of satellite measurements collected at different times—in 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. 5267:

the neighboring GPS band of 1559 to 1610 MHz. In 2004, the FCC adopted the OOBE agreement in its authorization for LightSquared to deploy a ground-based network ancillary to their satellite system – known as the Ancillary Tower Components (ATCs) – "We will authorize MSS ATC subject to conditions that ensure that the added terrestrial component remains ancillary to the principal MSS offering. We do not intend, nor will we permit, the terrestrial component to become a stand-alone service." This authorization was reviewed and approved by the U.S. Interdepartment Radio Advisory Committee, which includes the

1124: 341: 3749: 1004: 5601: 3461:(00:00:19 TAI on August 22, 1999). It happened the second time at 23:59:42 UTC on April 6, 2019. To determine the current Gregorian date, a GPS receiver must be provided with the approximate date (to within 3,584 days) to correctly translate the GPS date signal. To address this concern in the future the modernized GPS civil navigation (CNAV) message will use a 13-bit field that only repeats every 8,192 weeks (157 years), thus lasting until 2137 (157 years after GPS week zero). 2582:

GPS's mission capabilities, enabling U.S. Space Force to greatly enhance GPS operational services to U.S. combat forces, civil partners and myriad domestic and international users. The GPS OCX program also will reduce cost, schedule and technical risk. It is designed to provide 50% sustainment cost savings through efficient software architecture and Performance-Based Logistics. In addition, GPS OCX is expected to cost millions less than the cost to upgrade OCS while providing four times the capability.

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broadcasting from space to ground, and at power levels commensurate with mobile satellite services. As regulated under the FCC's Part 15 rules, GPS receivers are not warranted protection from signals outside GPS-allocated spectrum. 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.

5589: 5577: 2797: 3211: 4626: 277: 972:—detecting time slowing in a strong gravitational field using accurate atomic clocks placed in orbit inside artificial satellites. Special and general relativity predicted that the clocks on GPS satellites, as observed by those on Earth, run 38 microseconds faster per day than those on the Earth. The design of GPS corrects for this difference; because without doing so, GPS calculated positions would accumulate errors of up to 10 kilometers per day (6 mi/d). 3231: 18691: 2468: 4707: 2345: 2722: 2266: 1996: 3581:, which contains coarse orbit and status information for up to 32 satellites in the constellation as well as data related to error correction. Thus, to obtain an accurate satellite location from this transmitted message, the receiver must demodulate the message from each satellite it includes in its solution for 18 to 30 seconds. To collect all transmitted almanacs, the receiver must demodulate the message for 732 to 750 seconds or 4617:

satellites alone is unlikely to be accurate enough. Data from more satellites can help because of the tendency for random errors to cancel out and also by giving a larger spread between the sphere centers. But at the same time, more spheres will not generally intersect at one point. Therefore, a near intersection gets computed, typically via least squares. The more signals available, the better the approximation is likely to be.

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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 satellite's signal, it identifies it by its distinct C/A code pattern. There can be a delay of up to 30 seconds before the first estimate of position because of the need to read the ephemeris data.

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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.

906: 1309: 2061:) is constant and independent of the satellite speed, the time delay between when the satellite transmits a signal and the ground station receives it is proportional to the distance from the satellite to the ground station. With the distance information collected from multiple ground stations, the location coordinates of any satellite at any time can be calculated with great precision. 265: 836:, and similar agencies in other countries began to broadcast local GPS corrections, reducing the effect of both SA degradation and atmospheric effects (that military receivers also corrected for). The US military had also developed methods to perform local GPS jamming, meaning that the ability to globally degrade the system was no longer necessary. As a result, President 5565: 3602:(CDMA) so receivers can distinguish individual satellites from each other. The system uses two distinct CDMA encoding types: the coarse/acquisition (C/A) code, which is accessible by the general public, and the precise (P(Y)) code, which is encrypted so that only the U.S. military and other NATO nations who have been given access to the encryption code can access it. 1974:(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. 5090: 1154:) satellite used for geodetic surveying. The SECOR system included three ground-based transmitters at known locations that would send signals to the satellite transponder in orbit. A fourth ground-based station, at an undetermined position, could then use those signals to fix its location precisely. The last SECOR satellite was launched in 1969. 2675: 2112:(TOF) values, which are (given the speed of light) approximately equivalent to receiver-satellite ranges plus time difference between the receiver and GPS satellites multiplied by speed of light, which are called pseudo-ranges. The receiver then computes its three-dimensional position and clock deviation from the four TOFs. 5410:) was developed at the same time as GPS, but suffered from incomplete coverage of the globe until the mid-2000s. GLONASS reception in addition to GPS can be combined in a receiver thereby allowing for additional satellites available to enable faster position fixes and improved accuracy, to within two meters (6.6 ft). 8450: 4613:(more generally, true-range multilateration). Signals from at minimum three satellites are required, and their three spheres would typically intersect at two points. One of the points is the location of the receiver, and the other moves rapidly in successive measurements and would not usually be on Earth's surface. 5250:"must use receivers that reasonably discriminate against reception of signals outside their allocated spectrum". 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. 3015:: It is possible to aggregate GPS data from multiple users to understand movement patterns, common trajectories and interesting locations. GPS data is today used in transportation and disaster engineering to forecast mobility in normal and evacuation situations (e.g., hurricanes, wildfires, earthquakes). 5227:

Enhancement methods of improving accuracy rely on external information being integrated into the calculation process. There are many such systems in place and they are generally named or described based on how the GPS sensor receives the information. Some systems transmit additional information about

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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

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In 1960, the Air Force proposed a radio-navigation system called MOSAIC (MObile System for Accurate ICBM Control) that was essentially a 3-D LORAN. A follow-on study, Project 57, was performed in 1963 and it was "in this study that the GPS concept was born". That same year, the concept was pursued as

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Services, to use their allocated frequencies for an integrated satellite-terrestrial service. In 2002, the U.S. GPS Industry Council came to an out-of-band-emissions (OOBE) agreement with LightSquared to prevent transmissions from LightSquared's ground-based stations from emitting transmissions into

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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 37,500 bits long. At a transmission rate of

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The GPS navigation message includes the difference between GPS time and UTC. As of January 2017, GPS time is 18 seconds ahead of UTC because of the leap second added to UTC on December 31, 2016. Receivers subtract this offset from GPS time to calculate UTC and specific time zone values. New GPS

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The project remained delayed in 2023, and was (as of June 2023) 73% over its original estimated budget. In late 2023, Frank Calvelli, the assistant secretary of the Air Force for space acquisitions and integration, stated that the project was estimated to go live some time during the summer of 2024.

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oversaw GPS policy matters from 1996 to 2004. After that, the National Space-Based 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

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anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. It does not require the user to transmit any data, and operates independently of any telephone or Internet reception, though these technologies can enhance the usefulness of the GPS positioning

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Hadas, T.; Krypiak-Gregorczyk, A.; Hernández-Pajares, M.; Kaplon, J.; Paziewski, J.; Wielgosz, P.; Garcia-Rigo, A.; Kazmierski, K.; Sosnica, K.; Kwasniak, D.; Sierny, J.; Bosy, J.; Pucilowski, M.; Szyszko, R.; Portasiak, K.; Olivares-Pulido, G.; Gulyaeva, T.; Orus-Perez, R. (November 2017). "Impact

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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

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Three satellites (labeled as "stations" A, B, C) have known locations. The true times it takes for a radio signal to travel from each satellite to the receiver are unknown, but the true time differences are known. Then, each time difference locates the receiver on a branch of a hyperbola focused on

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If the almanac information has previously been acquired, the receiver picks the satellites to listen for by their PRNs, unique numbers in the range 1 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

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The user segment (US) is composed of hundreds of thousands of U.S. 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. In general, GPS receivers are composed of an antenna, tuned

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The U.S. 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

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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 U.S. Navy and U.S. Air Force were developing their own technologies in parallel to solve what was

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rules. As indicated in the manuals of GPS-enabled devices sold in the United States, as a Part 15 device, it "must accept any interference received, including interference that may cause undesired operation". With respect to GPS devices in particular, the FCC states that GPS receiver manufacturers

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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

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The L3 signal at a frequency of 1.38105 GHz 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 Earth's atmosphere and near

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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.

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GPS's vulnerability to jamming is a threat that continues to grow as jamming equipment and experience grows. GPS signals have been reported to have been jammed many times over the years for military purposes. Russia seems to have several objectives for this approach, such as intimidating neighbors

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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

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The U.S. government controls the export of some civilian receivers. All GPS receivers capable of functioning above 60,000 ft (18 km) above sea level and 1,000 kn (500 m/s; 2,000 km/h; 1,000 mph), or designed or modified for use with unmanned missiles and aircraft, are

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issued a directive making GPS freely available for civilian use, once it was sufficiently developed, as a common good. The first Block II satellite was launched on February 14, 1989, and the 24th satellite was launched in 1994. The GPS program cost at this point, not including the cost of the

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In fact, the ship is unlikely to be at precisely 0m, because of tides and other factors which create a discrepancy between mean sea level and actual sea level. In the open ocean, high and low tide typically only differ by about 0.6m, but there are locations closer to land where they can differ by

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The ephemeris is updated every 2 hours and is sufficiently stable for 4 hours, with provisions for updates every 6 hours or longer in non-nominal conditions. The almanac is updated typically every 24 hours. Additionally, data for a few weeks following is uploaded in case of transmission

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field in the C/A and P(Y) navigation messages, and so it becomes zero again every 1,024 weeks (19.6 years). GPS week zero started at 00:00:00 UTC (00:00:19 TAI) on January 6, 1980, and the week number became zero again for the first time at 23:59:47 UTC on August 21, 1999

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from everywhere on the Earth's surface (see animation at right). The result of this objective is that the four satellites are not evenly spaced (90°) apart within each orbit. In general terms, the angular difference between satellites in each orbit is 30°, 105°, 120°, and 105° apart, which sum to

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in 2000. When Selective Availability was discontinued, GPS was accurate to about 5 meters (16 ft). GPS receivers that use the L5 band have much higher accuracy of 30 centimeters (12 in), while those for high-end applications such as engineering and land surveying are accurate to within

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The FCC adopted rules in February 2003 that allowed Mobile Satellite Service (MSS) licensees such as LightSquared to construct a small number of ancillary ground-based towers in their licensed spectrum to "promote more efficient use of terrestrial wireless spectrum". In those 2003 rules, the FCC

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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 or from intentional signal degradation through

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OCS will continue to be the ground control system of record until the new segment, Next Generation GPS Operation Control System (OCX), is fully developed and functional. The US Department of Defense has claimed that the new capabilities provided by OCX will be the cornerstone for revolutionizing

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The GPS implements two major corrections to its time signals for relativistic effects: one for relative velocity of satellite and receiver, using the special theory of relativity, and one for the difference in gravitational potential between satellite and receiver, using general relativity. The

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On September 14, 2011, the U.S. 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 missed major milestones and pushed its launch into 2021, 5 years past the original deadline.

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Bancroft's 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 single-variable quadratic equation. Bancroft's method provides one or two solutions for the unknown

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In practice, there are many sources of inaccuracy besides clock bias, including random errors as well as the potential for precision loss from subtracting numbers close to each other if the centers of the spheres are relatively close together. This means that the position calculated from three

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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

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Since its deployment, the U.S. 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

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On February 12, 2019, four founding members of the project were awarded the Queen Elizabeth Prize for Engineering with the chair of the awarding board stating: "Engineering is the foundation of civilisation; there is no other foundation; it makes things happen. And that's exactly what today's

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Since the equations have four unknowns —the three components of GPS receiver position and the clock bias—signals from at least four satellites are necessary to attempt solving these equations. They can be solved by algebraic or numerical methods. Existence and uniqueness of GPS solutions are

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The spectrum allocated for GPS L1 use by the FCC is 1559 to 1610 MHz, while the spectrum allocated for satellite-to-ground use owned by Lightsquared is the Mobile Satellite Service band. Since 1996, the FCC has authorized licensed use of the spectrum neighboring the GPS band of 1525 to

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Navstar is often erroneously considered an acronym for "NAVigation System using Timing And Ranging" but was never considered as such by the GPS Joint Program Office (TRW may have once advocated for a different navigational system that used that acronym). With the individual satellites being

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GPS receiver manufacturers design GPS receivers to use spectrum beyond the GPS-allocated band. In some cases, GPS receivers are designed to use up to 400 MHz of spectrum in either direction of the L1 frequency of 1575.42 MHz, because mobile satellite services in those regions are

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that make observers on the Earth perceive a different time reference with respect to the transmitters in orbit. The L1 carrier is modulated by both the C/A and P codes, while the L2 carrier is only modulated by the P code. The P code can be encrypted as a so-called

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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 (i.e., the receiver measures true ranges to the satellites rather than range

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GPS has become a widely deployed and useful tool for commerce, scientific uses, tracking, and surveillance. GPS's accurate time facilitates everyday activities such as banking, mobile phone operations, and even the control of power grids by allowing well synchronized hand-off switching.

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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

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among others, had to be resolved. A team led by Harold L. Jury of Pan Am Aerospace Division in Florida from 1970 to 1973, used real-time data assimilation and recursive estimation to do so, reducing systematic and residual errors to a manageable level to permit accurate navigation.

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code (sequence of ones and zeros) that is known to the receiver. By time-aligning a receiver-generated version and the receiver-measured 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

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each day. 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.

3380:, GPS-guided munitions provided to Ukraine by NATO countries experienced significant failure rates as a result of Russian electronic warfare. Excalibur artillery shells efficiency rate hitting targets dropped from 70% to 6% as Russia adapted its electronic warfare activities. 4816: 1162:

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 multi-service program. Satellite orbital position errors, induced by variations in the

1957:(Col. USAF, ret.) was inducted into the U.S. Air Force Space and Missile Pioneers Hall of Fame at Lackland A.F.B., 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. 897: 2667:

port at 4,800 bit/s speed. Data is actually sent at a much lower rate, which limits the accuracy of the signal sent using RTCM. Receivers with internal DGPS receivers can outperform those using external RTCM data. As of 2006, even low-cost units commonly include

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gives the position of the receiver along with the difference between the time kept by the receiver's on-board clock and the true time-of-day, thereby eliminating the need for a more precise and possibly impractical receiver based clock. Applications for GPS such as

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services by private industry to improve civilian accuracy. Moreover, the U.S. military was developing technologies to deny GPS service to potential adversaries on a regional basis. Selective Availability was removed from the GPS architecture beginning with GPS-III.

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is the receiver's 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 message's transit time is

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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 on the open ocean usually has a known elevation

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information. It provides critical positioning capabilities to military, civil, and commercial users around the world. Although the United States government created, controls and maintains the GPS system, it is freely accessible to anyone with a GPS receiver.

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OCS successfully replaced the legacy 1970s-era 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 U.S. armed forces.

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As of early 2015, high-quality Standard Positioning Service (SPS) GPS receivers provided horizontal accuracy of better than 3.5 meters (11 ft), although many factors such as receiver and antenna quality and atmospheric issues can affect this accuracy.

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while undermining confidence in their reliance on American systems, promoting their GLONASS alternative, disrupting Western military exercises, and protecting assets from drones. China uses jamming to discourage US surveillance aircraft near the contested

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that are synchronized with one another and with the reference atomic clocks at the ground control stations; any drift of the clocks aboard the satellites from the reference time maintained on the ground stations is corrected regularly. Since the speed of

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On December 6, 2018, Gladys West was inducted into the Air Force Space and Missile Pioneers Hall of Fame in recognition of her work on an extremely accurate geodetic Earth model, which was ultimately used to determine the orbit of the GPS constellation.

1069:, 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 ultra-secrecy at that time. The 1057:

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.

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Early the next year, Frank McClure, the deputy director of the APL, asked Guier and Weiffenbach to investigate the inverse problem: pinpointing the user's location, given the satellite's. (At the time, the Navy was developing the submarine-launched

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All satellites broadcast at the same two frequencies, 1.57542 GHz (L1 signal) and 1.2276 GHz (L2 signal). The satellite network uses a CDMA spread-spectrum technique where the low-bitrate message data is encoded with a high-rate

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Chwedczuk, Katarzyna; Cienkosz, Daniel; Apollo, Michal; Borowski, Lukasz; Lewinska, Paulina; Guimarães Santos, Celso Augusto; Eborka, Kennedy; Kulshreshtha, Sandeep; Romero-Andrade, Rosendo; Sedeek, Ahmed; Liibusk, Aive; MacIuk, Kamil (2022).

5348:(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 FCC's action. 16582: 2187:

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

1939:, conceived the present satellite-based system in the early 1960s and developed it in conjunction with the U.S. Air Force. Parkinson served twenty-one years in the Air Force, from 1957 to 1978, and retired with the rank of colonel. 3716:(PRN) sequence that is different for each satellite. The receiver must be aware of the PRN codes for each satellite to reconstruct the actual message data. The C/A code, for civilian use, transmits data at 1.023 million 16519: 913:

The GPS project was launched in the United States in 1973 to overcome the limitations of previous navigation systems, combining ideas from several predecessors, including classified engineering design studies from the 1960s. The

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Both the equations for four satellites, or the least squares equations for more than four, are non-linear and need special solution methods. A common approach is by iteration on a linearized form of the equations, such as the

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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 50 years ago".

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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

2897:(FCC) mandated the feature in either the handset or in the towers (for use in triangulation) in 2002 so emergency services could locate 911 callers. Third-party software developers later gained access to GPS APIs from 16131: 15126: 10278: 5138:

Leick et al. (2015) states that "Bancroft's (1985) solution is a very early, if not the first, closed-form solution." Other closed-form solutions were published afterwards, although their adoption in practice is unclear.

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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 "fenced-in")

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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.

2531:(2 SOPS) of the U.S. Space Force. Then 2 SOPS contacts each GPS satellite regularly with a navigational update using dedicated or shared (AFSCN) ground antennas (GPS dedicated ground antennas are located at 11673:"FCC Docket File Number: SATASG2001030200017, "Mobile Satellite Ventures LLC Application for Assignment and Modification of Licenses and for Authority to Launch and Operate a Next-Generation Mobile Satellite System"" 4379: 2885:: clock synchronization enables time transfer, which is critical for synchronizing its spreading codes with other base stations to facilitate inter-cell handoff and support hybrid GPS/cellular position detection for 16156: 1283:

executive committee is chaired jointly by the Deputy Secretaries of Defense and Transportation. Its membership includes equivalent-level officials from the Departments of State, Commerce, and Homeland Security, the

3271:, require all radios within a network to have the same time input to their internal clocks (+/-4 seconds in the case of SINCGARS) to be on the correct frequency at a given time. Military GPS receivers, such as the 10901: 873: in) and can even provide sub-millimeter accuracy with long-term measurements. Consumer devices such as smartphones can be accurate to 4.9 m (16 ft) or better when used with assistive services like 1659:

announced that GPS would be made available for civilian uses once it was completed, although it had been publicly known as early as 1979, that the CA code (Coarse/Acquisition code) would be available to civilian

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has mounted several major jamming operations near its border with South Korea and offshore, disrupting flights, shipping and fishing operations. Iranian Armed Forces disrupted the civilian airliner plane Flight

2592:

Built on a flexible architecture that can rapidly adapt to the changing needs of today's and future GPS users allowing immediate access to GPS data and constellation status through secure, accurate and reliable

2687:

protocol. Although this protocol is officially defined by the National Marine Electronics Association (NMEA), references to this protocol have been compiled from public records, allowing open source tools like

16378: 16201: 16002: 15148: 7722: 11992: 11960:"Testimony of Jeff Carlisle, LightSquared Executive Vice President of Regulatory Affairs and Public Policy to U.S. House Subcommittee on Aviation and Subcommittee on Coast Guard and Maritime Transportation" 16348: 5085:{\displaystyle \left({\hat {x}},{\hat {y}},{\hat {z}},{\hat {b}}\right)={\underset {\left(x,y,z,b\right)}{\arg \min }}\sum _{i}\left({\sqrt {(x-x_{i})^{2}+(y-y_{i})^{2}+(z-z_{i})^{2}}}+bc-p_{i}\right)^{2}} 1695:

In 1991, DARPA's project to create a miniature GPS receiver successfully ended, replacing the previous 16 kg (35 lb) military receivers with a 1.25 kg (2.8 lb) all-digital handheld GPS

11676: 5232:), others provide direct measurements of how much the signal was off in the past, while a third group provides additional navigational or vehicle information to be integrated into the calculation process. 17716: 16527: 16468: 11893: 4772:

with large differences compared to the true distances to the satellites. Therefore, in practice, the time difference between the receiver clock and the satellite time is defined as an unknown clock bias

3720:

per second, whereas the P code, for U.S. military use, transmits at 10.23 million chips per second. The actual internal reference of the satellites is 10.22999999543 MHz to compensate for

1830:

On January 11, 2010, an update of ground control systems caused a software incompatibility with 8,000 to 10,000 military receivers manufactured by a division of Trimble Navigation Limited of Sunnyvale,

4461: 946:

on the creation of the mathematical geodetic Earth model is credited as instrumental in the development of computational techniques for detecting satellite positions with the precision needed for GPS.

2076:; However, at a minimum, four satellites must be in view of the receiver for it to compute four unknown quantities (three position coordinates and the deviation of its own clock from satellite time). 1254:

signing 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 U.S. Secretary of Defense,

16599: 16373: 15471: 3405:

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

892: 16196: 4109: 6632:

Jury, H L, 1973, Application of Kalman Filter to Real-Time Navigation using Synchronous Satellites, Proceedings of the 10th International Symposium on Space Technology and Science, Tokyo, 945–952.

3198:

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

17319: 16999: 16191: 15888: 15880: 14022: 11823: 3809:

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

3283:

within a radio network to properly input an accurate time to said radios internal clock. More modern military radios have internal GPS receivers that syncronize the internal clock automatically.

16388: 16114: 15696: 15674: 4577:(GDOP) factors, calculated from the relative sky directions of the satellites used. The receiver location is expressed in a specific coordinate system, such as latitude and longitude using the 3248:

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

2602:

Provides significant information assurance improvements over the current program including detecting and preventing cyber attacks, while isolating, containing and operating during such attacks.

6935:

The Global Positioning System Assessing National Policies, by Scott Pace, Gerald P. Frost, Irving Lachow, David R. Frelinger, Donna Fossum, Don Wassem, Monica M. Pinto, Rand Corporation, 1995,

5325:, airline pilots with the type of systems that would be affected "may go off course and not even realize it". The problems could also affect the Federal Aviation Administration upgrade to the 18400: 3009:: the use of RTK GPS has significantly improved several mining operations such as drilling, shoveling, vehicle tracking, and surveying. RTK GPS provides centimeter-level positioning accuracy. 10752: 17753: 16884: 16869: 16559: 6067: 3571:

The first subframe of each frame encodes the week number and the time within the week, as well as the data about the health of the satellite. The second and the third subframes contain the

17647: 17461: 16715: 16642: 16169: 16144: 14184: 4550: 11788:"FCC Order, Granted LightSquared Subsidiary LLC, a Mobile Satellite Service licensee in the L-Band, a conditional waiver of the Ancillary Terrestrial Component "integrated service" rule" 8040: 2399:, and also includes the payload adapters to the boosters required to launch them into orbit. The GPS design originally called for 24 SVs, eight each in three approximately circular 17419: 17031: 16587: 16547: 16507: 15910: 14015: 9019:

Glaser, Susanne; Fritsche, Mathias; Sośnica, Krzysztof; Rodríguez-Solano, Carlos Javier; Wang, Kan; Dach, Rolf; Hugentobler, Urs; Rothacher, Markus; Dietrich, Reinhard (December 2015).

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minutes) to complete. The message structure has a basic format of a 1500-bit-long frame made up of five subframes, each subframe being 300 bits (6 seconds) long. Subframes 4 and 5 are

17406: 17359: 17244: 15972: 15935: 10845: 4026: 3966: 11609:"Federal Communications Commission Report and Order In the Matter of Fixed and Mobile Services in the Mobile Satellite Service Bands at 1525–1559 MHz and 1626.5–1660.5 MHz" 3438:

acceleration of the satellite could also be computed independently as a correction, depending on purpose, but normally the effect is already dealt with in the first two corrections.

1838:

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.

17061: 16667: 16418: 15101: 5940: 3286:

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

2348:

GPS II underwent a four-month series of qualification tests in the AEDC Mark I Space Chamber to determine whether the satellite could withstand extreme heat and cold in space, 1985.

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Sivalingam, Prahaladhan; Asirvatham, David; Marjani, Mohsen; Syed Masood, Jafar Ali Ibrahim; Chakravarthy, N. S. Kalyan; Veerisetty, Gopinath; Lestari, Martha Tri (April 1, 2024).

2353: 2164:). 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. 10282: 2443:

Orbiting at an altitude of approximately 20,200 km (12,600 mi); orbital radius of approximately 26,600 km (16,500 mi), each SV makes two complete orbits each

2156:

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

6036: 4785:(or spherical cone), 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 hypercones. 2641: 918:

developed the system, which originally used 24 satellites, for use by the United States military, and became fully operational in 1993. Civilian use was allowed from the 1980s.

3429:

that the atomic clocks in GPS transmitters experience. Most receivers lose some accuracy in their interpretation of the signals and are only accurate to about 100 nanoseconds.

16574: 16413: 16326: 7468: 6875: 3911: 1184:

associated with the name Navstar (as with the predecessors Transit and Timation), a more fully encompassing name was used to identify the constellation of Navstar satellites,

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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.

17439: 17194: 17189: 16032: 15644: 11510: 1127:

Navigation Technology Satellite – II (Timation IV): NTS-II, the first satellite completely designed and built by NRL under GPS Joint Program funding. Launched June 23, 1977.

12268: 3218: 17199: 15959: 15413: 12081: 10209: 7070: 880:

As of July 2023, 18 GPS satellites broadcast L5 signals, which are considered pre-operational prior to being broadcast by a full complement of 24 satellites in 2027.

5116:

One closed-form solution to the above set of equations was developed by S. Bancroft. Its properties are well known; in particular, proponents claim it is superior in low-

814: 16027: 15807: 5321:

The FCC and LightSquared have each made public commitments to solve the GPS interference issue before the network is allowed to operate. According to Chris Dancy of the

11544:

Selective Availability ended a few minutes past midnight EDT after the end of May 1, 2000. The change occurred simultaneously across the entire satellite constellation.

1637:

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

16284: 14204: 11959: 10179: 10004: 5345: 3726:

P(Y) code that is only available to military equipment with a proper decryption key. Both the C/A and P(Y) codes impart the precise time-of-day to the user.

2523:, along with shared NGA monitor stations operated in England, Argentina, Ecuador, Bahrain, Australia and Washington DC. The tracking information is sent to the MCS at 1761:

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

12406: 10065: 7730: 18250: 7271: 3033:: navigators value digitally precise velocity and orientation measurements, as well as precise positions in real-time with a support of orbit and clock corrections. 2966:

including the daily and sub-daily polar motion, and length-of-day variabilities, Earth's center-of-mass - geocenter motion, and low-degree gravity field parameters.

1774:

On May 2, 2000 "Selective Availability" was discontinued as a result of the 1996 executive order, allowing civilian users to receive a non-degraded signal globally.

18287: 16899: 15228: 15195: 9898: 8629: 6139: 5131:(i.e., the pseudoinverse) to find a solution. A case has been made that iterative methods, such as the Gauss–Newton algorithm approach for solving over-determined 18602: 11085: 7231: 2585:

The GPS OCX program represents a critical part of GPS modernization and provides significant information assurance improvements over the current GPS OCS program.

2236:

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.

12061: 11999: 11672: 9370:

Braund, Taylor A.; Zin, May The; Boonstra, Tjeerd W.; Wong, Quincy J. J.; Larsen, Mark E.; Christensen, Helen; Tillman, Gabriel; O'Dea, Bridianne (May 4, 2022).

2570:, so receivers do not use it. After the maneuver, engineers track the new orbit from the ground, upload the new ephemeris, and mark the satellite healthy again. 11885: 1246:

Initially, the highest-quality signal was reserved for military use, and the signal available for civilian use was intentionally degraded, in a policy known as

16151: 13259: 12028: 7986: 7583: 6993: 6939: 8576: 7669: 3413:

units may not show the correct UTC time until after receiving the UTC offset message. The GPS-UTC offset field can accommodate 255 leap seconds (eight bits).

17813: 17738: 11556: 9864: 8603: 6578: 3824:

Processing of the navigation message enables the determination of the time of transmission and the satellite position at this time. For more information see

10035: 7126: 6191: 2064:

Each GPS satellite carries an accurate record of its own position and time, and broadcasts that data continuously. Based on data received from multiple GPS

12237: 11573: 9935: 4698:

at a pair of satellites. With additional satellites, the multiple intersections are not necessarily unique, and a best-fitting solution is sought instead.

2326:

from space, and each GPS receiver uses these signals to calculate its three-dimensional location (latitude, longitude, and altitude) and the current time.

1851:

AFSPC Vice Commander Lt. Gen. DT Thompson presents Gladys West with an award as she is inducted into the Air Force Space and Missile Pioneers Hall of Fame.

1291:. Components of the executive office of the president participate as observers to the executive committee, and the FCC chairman participates as a liaison. 9787: 7560: 4768:

The clock in the receiver is usually not of the same quality as the ones in the satellites and will not be accurately synchronized to them. This produces

4592:

The GPS equations can be solved by numerical and analytical methods. Geometrical interpretations can enhance the understanding of these solution methods.

18745: 18735: 18229: 9761: 3214:

AN/PRC-119F SINCGARS radio, which requires accurate clock time supplied by an external GPS system to enable frequency hopping operation with other radios

2108:

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

12131: 10122: 18740: 16966: 16012: 14029: 13481: 13412: 11827: 6849: 5882: 3123:: realization and densification of the terrestrial reference frames in the framework of Global Geodetic Observing System. Co-location in space between 1788:

updated the national policy and replaced the executive board with the National Executive Committee for Space-Based Positioning, Navigation, and Timing.

7529: 18260: 18224: 13438: 13387: 13356: 3337: 3191:

export licenses. This rule applies even to otherwise purely civilian units that only receive the L1 frequency and the C/A (Coarse/Acquisition) code.

3012: 2244:, and the elevation of an aircraft may be known. Some GPS receivers may use additional clues or assumptions such as reusing the last known altitude, 11059: 9505:

Strugarek, Dariusz; Sośnica, Krzysztof; Arnold, Daniel; Jäggi, Adrian; Zajdel, Radosław; Bury, Grzegorz; Drożdżewski, Mateusz (September 30, 2019).

8504: 6001: 4777:. The equations are then solved simultaneously for the receiver position and the clock bias. The solution space can be seen as a four-dimensional 15121: 14315: 10760: 10566: 10365: 8160: 7399: 5402:

Following the United States' deployment of GPS, other countries have also developed their own satellite navigation systems. These systems include:

5148: 4120: 3476:

Two different encodings are used: a public encoding that enables lower resolution navigation, and an encrypted encoding used by the U.S. military.

3006: 1016: 7319: 18234: 17869: 16609: 10722: 9963: 8129: 6956: 1243:

user equipment but including the costs of the satellite launches, has been estimated at US$ 5 billion (equivalent to $ 10 billion in 2023).

1120:

Project 621B, which had "many of the attributes that you now see in GPS" and promised increased accuracy for Air Force bombers as well as ICBMs.

700: 12211: 11730: 10978: 6545: 5805: 854:

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

18654: 17074: 16617: 16564: 16455: 16316: 16289: 16181: 14376: 14371: 13733: 11916: 11860: 11798: 11608: 10841: 8391: 8196: 8047: 5841: 4257: 11032: 8545:"GLOBAL POSITIONING SYSTEM: Updated Schedule Assessment Could Help Decision Makers Address Likely Delays Related to New Ground Control System" 6140:

National Research Council (U.S.). Committee on the Future of the Global Positioning System; National Academy of Public Administration (1995).

17783: 17711: 17667: 17509: 17504: 17491: 17414: 17401: 17346: 17336: 17331: 17216: 17154: 16835: 16825: 16745: 16604: 16393: 16368: 16214: 16139: 15900: 15895: 13212: 13205: 13198: 13191: 13184: 13177: 13170: 13163: 13156: 13149: 13142: 13135: 13128: 13121: 13114: 13107: 13100: 13093: 13086: 13079: 13072: 13065: 10258: 5280: 3409:(TAI) (TAI - GPS = 19 seconds). Periodic corrections are performed to the on-board clocks to keep them synchronized with ground clocks. 1880: 1806:

In 2005, the first modernized GPS satellite was launched and began transmitting a second civilian signal (L2C) for enhanced user performance.

12442: 7613: 4694:). Thus, from four pseudorange measurements, the receiver can be placed at the intersection of the surfaces of three hyperboloids each with 18255: 17677: 17324: 17296: 17281: 17276: 17249: 17221: 17121: 17116: 16532: 13045: 13038: 13031: 13024: 10812: 10540: 9669:

Sośnica, K.; Bury, G.; Zajdel, R. (March 16, 2018). "Contribution of Multi-GNSS Constellation to SLR-Derived Terrestrial Reference Frame".

8654: 7392: 6519: 1777:

In 2004, the United States government signed an agreement with the European Community establishing cooperation related to GPS and Europe's

7655: 5932: 2252:, or including information from the vehicle computer, to give a (possibly degraded) position when fewer than four satellites are visible. 18628: 18539: 17622: 17469: 17376: 17364: 17106: 17101: 17081: 17056: 16007: 14972: 13940: 13526: 13372: 13307: 11850:"FCC Order permitting mobile satellite services providers to provide an ancillary terrestrial component (ATC) to their satellite systems" 11762: 11171: 11132: 10088: 9462:

Strugarek, Dariusz; Sośnica, Krzysztof; Jäggi, Adrian (January 2019). "Characteristics of GOCE orbits based on Satellite Laser Ranging".

9175:

Khetarpaul, S.; Chauhan, R.; Gupta, S. K.; Subramaniam, L. V.; Nambiar, U. (2011). "Mining GPS data to determine interesting locations".

5451: 5108:

The GPS was initially developed assuming use of a numerical least-squares solution method—i.e., before closed-form solutions were found.

3817:. The signals are decoded after demodulation using addition of the Gold codes corresponding to the satellites monitored by the receiver. 522: 11213: 10607: 10148: 9266:

Zhao, Xilei; Xu, Yiming; Lovreglio, Ruggiero; Kuligowski, Erica; Nilsson, Daniel; Cova, Thomas J.; Wu, Alex; Yan, Xiang (June 1, 2022).

2119:

with origin at the Earth's center) and the offset of the receiver clock relative to the GPS time are computed simultaneously, using the

1982:

Laureates have done – they've made things happen. They've re-written, in a major way, the infrastructure of our world."

16537: 15684: 13252: 11647: 5790: 3356:, when Iraqi forces installed jamming devices on likely targets that emitted radio noise, disrupting reception of the weak GPS signal. 2915:: 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 2739: 2632:

GPS receivers come in a variety of formats, from devices integrated into cars, phones, and watches, to dedicated devices such as these.

2283: 2013: 1278:

GPS is owned and operated by the United States government as a national resource. The Department of Defense is the steward of GPS. The

690: 658: 8416: 7792: 7494: 6401: 6245: 6028: 2940:: measure and calculate the atmospheric pressure, wind speed and direction up to 27 km (89,000 ft) from the Earth's surface. 18574: 18562: 17456: 17381: 17304: 17239: 17211: 17184: 17179: 17174: 17169: 17021: 16976: 16956: 16906: 16856: 16813: 16808: 16795: 16783: 16778: 16763: 16758: 16735: 16725: 16697: 16692: 16687: 16657: 16637: 16480: 16331: 16311: 16249: 16244: 16089: 16019: 15977: 15820: 15815: 15523: 15320: 15295: 15250: 15233: 15215: 15205: 13397: 12322: 9931: 9894: 9587:

Sośnica, Krzysztof; Thaller, Daniela; Dach, Rolf; Steigenberger, Peter; Beutler, Gerhard; Arnold, Daniel; Jäggi, Adrian (July 2015).

8766: 8526: 8014: 6879: 6805: 3199: 2808:

Many civilian applications use one or more of GPS's three basic components: absolute location, relative movement, and time transfer.

794:

in 1973. The first prototype spacecraft was launched in 1978 and the full constellation of 24 satellites became operational in 1993.

6419: 2104:

A message that includes the time of transmission (TOT) of the code epoch (in GPS time scale) and the satellite position at that time

18532: 17793: 16629: 16119: 14306: 14221: 14164: 14159: 12475: 10388: 9094: 8858: 7761: 7469:"Press release: First Modernized GPS Satellite Built by Lockheed Martin Launched Successfully by the U.S. Air Force – Sep 26, 2005" 7347: 5976: 5284: 2837:

delays (recovery of the number of free electrons). Recovery of Earth surface displacements due to the atmospheric pressure loading.

668: 11531: 11507: 8179: 6307: 820:

As civilian GPS usage grew, there was increasing pressure to remove this error. The SA system was temporarily disabled during the

18525: 18292: 14904: 14179: 14174: 14169: 13561: 12260: 11495:

Proceedings of the 26th International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2013)

10999: 7651: 4753:. This configuration is distinct from the one described above, in which the spheres' radii were the unbiased or geometric ranges 2500: 2363: 1196: 1132: 12078: 10201: 8681:

and Implementation of Higher-Order Ionospheric Effects on Precise GNSS Applications: Higher-Order Ionospheric Effects in GNSS".

7066: 7044: 5221:

refers to techniques used to improve the accuracy of positioning information provided by the Global Positioning System or other

4391: 2503:) monitor stations. The flight paths of the satellites are tracked by dedicated U.S. Space Force monitoring stations in Hawaii, 18672: 17909: 16647: 16490: 16426: 15730: 14199: 13474: 8256: 5322: 4806:

Using more than four involves an over-determined system of equations with no unique solution; such a system can be solved by a

1971: 10931: 7096: 5159:

selective availability, which limited accuracy to ≈ 6–12 m (20–40 ft), but has been switched off since May 1, 2000.

824:, as a shortage of military GPS units meant that many US soldiers were using civilian GPS units sent from home. In the 1990s, 18395: 17951: 17474: 14689: 13245: 12426: 12380: 12359: 11246: 11207: 11165: 11126: 10706: 10672: 10645: 10601: 9112: 8297: 7969: 7293: 7193: 7159: 6728: 6686: 6185: 6151: 5535: 1898: 1863:, the US's most prestigious aviation award. This team combines researchers from the Naval Research Laboratory, the USAF, the 648: 11966: 11252: 10171: 4046: 18622: 18010: 15772: 15723: 14618: 10336: 10057: 8347: 1074: 7442: 6692: 2692:

to read the protocol without violating intellectual property laws. Other proprietary protocols exist as well, such as the

2318:

The current GPS consists of three major segments. These are the space segment, a control segment, and a user segment. The

1827:

allayed fears of GPS failure, saying: "There's only a small risk we will not continue to exceed our performance standard."

1179:. It was at this meeting that the real synthesis that became GPS was created. Later that year, the DNSS program was named 1175:

During Labor Day weekend in 1973, a meeting of about twelve military officers at the Pentagon discussed the creation of a

18557: 16161: 15952: 14699: 13382: 8230: 7257: 5830: 5442: 5344:

On February 14, 2012, the FCC moved to bar LightSquared's planned national broadband network after being informed by the

5222: 3568:. Each 30-second frame begins precisely on the minute or half-minute as indicated by the atomic clock on each satellite. 1139:(Time Navigation) satellites, first launched in 1967, second launched in 1969, with the third in 1974 carrying the first 791: 14366: 10867: 10000: 9887: 7692: 6089: 628: 18725: 18704: 16219: 13726: 13361: 11093: 9842: 8832: 8551: 7217: 6911: 6493: 6471: 5416: 4574: 3336:, an X-ray sensor, a dosimeter, and an electromagnetic pulse (EMP) sensor (W-sensor), that form a major portion of the 3272: 2472: 2196:

of the signals received to compute velocity accurately. More advanced navigation systems use additional sensors like a

1086: 429: 12058: 9372:"Smartphone Sensor Data for Identifying and Monitoring Symptoms of Mood Disorders: A Longitudinal Observational Study" 6284: 3133:: self-navigating, autonomous robots using GPS sensors, which calculate latitude, longitude, time, speed, and heading. 2134:

and height relative to an ellipsoidal Earth model. The height may then be further converted to height relative to the

1108:

To increase the survivability of ICBMs, there was a proposal to use mobile launch platforms (comparable to the Soviet

17988: 16256: 15992: 15433: 14246: 13596: 13467: 12311: 11699:"U.S. GPS Industry Council Petition to the FCC to adopt OOBE limits jointly proposed by MSV and the Industry Council" 11465: 10517: 8433: 7367: 6444: 6372: 6222: 5288: 5242: 3790:

magazine reports that the latest testing (June 2011) confirms "significant jamming" of GPS by LightSquared's system.

3456:, the GPS date is expressed as a week number and a seconds-into-week number. The week number is transmitted as a ten- 3260: 3188: 2894: 2820: 2761: 2599:

Enables new modernized signals (L1C, L2C, and L5) and has M-code capability, which the legacy system is unable to do.

2403:, but this was modified to six orbital planes with four satellites each. The six orbit planes have approximately 55° 2305: 2035: 754: 728: 12036: 8368: 7990: 7591: 6989: 6936: 6754:

Hegarty, Christopher J.; Chatre, Eric (December 2008). "Evolution of the Global Navigation SatelliteSystem (GNSS)".

6650: 6603: 2360:

from a given point on the Earth's surface changes with time. The point in this example is in Golden, Colorado, USA (

18730: 18519: 16336: 15706: 15701: 14481: 14345: 7677: 6571: 6143:

The global positioning system: a shared national asset: recommendations for technical improvements and enhancements

5525: 5330: 1817: 1199:, renamed to Air Force Geophysical Research Lab (AFGRL) in 1974. AFGRL developed the Klobuchar model for computing 1192:" prototype satellites were launched between 1978 and 1985 (an additional unit was destroyed in a launch failure). 9860: 9817: 8888:

Zajdel, Radosław; Sośnica, Krzysztof; Bury, Grzegorz; Dach, Rolf; Prange, Lars; Kazmierski, Kamil (January 2021).

6280:

Relativistische Zeitdilatation eines künstlichen Satelliten (Relativistic time dilation of an artificial satellite

6059: 4469: 3401:. The difference is that GPS time is not corrected to match the rotation of the Earth, so it does not contain new 2435:

or almost the same locations every day. The orbits are arranged so that at least six satellites are always within

18552: 18000: 15679: 15210: 14965: 14557: 14340: 13571: 12292: 10027: 9507:"Determination of Global Geodetic Parameters Using Satellite Laser Ranging Measurements to Sentinel-3 Satellites" 7118: 6175: 5794: 5276: 5198: 5117: 2596:

Provides the warfighter with more secure, actionable and predictive information to enhance situational awareness.

2356:

A visual example of a 24-satellite GPS constellation in motion with the Earth rotating. Notice how the number of

1856: 1751: 996:, they could pinpoint where the satellite was along its orbit. The Director of the APL gave them access to their 833: 12233: 11580: 9924: 7552: 7017: 5966: 5903: 3021:: location determines what content to display; for instance, information about an approaching point of interest. 1732:(IOC), with a full constellation (24 satellites) available and providing the Standard Positioning Service (SPS). 813:; however, initially this civilian use was limited to an average accuracy of 100 meters (330 ft) by use of 16672: 16401: 16341: 14236: 13930: 13511: 13377: 13292: 9783: 8728:"Impact of loading displacements on SLR-derived parameters and on the consistency between GNSS and SLR results" 5500: 5425: 5268: 2743: 2287: 2017: 1778: 1739:(AFSPC) in April 1995, signifying full availability of the military's secure Precise Positioning Service (PPS). 1729: 851:, the US government announced that the next generation of GPS satellites would not include the feature at all. 514: 11756:"Statement of Julius P. Knapp, Chief, Office of Engineering and Technology, Federal Communications Commission" 9753: 6642: 5909: 3976: 3916: 1146:

Another important predecessor to GPS came from a different branch of the United States military. In 1964, the

18636: 18185: 15063: 14653: 13945: 13719: 13556: 13531: 13407: 13392: 12139: 10231: 10118: 6365:

Transit to Tomorrow. Fifty Years of Space Research at The Johns Hopkins University Applied Physics Laboratory

5480: 5438: 3713: 3599: 3276: 2669: 2528: 1964: 1671: 530: 12098: 8075: 7919:

Fang, B.T. (1992). "Comments on "Existence and uniqueness of GPS solutions" by J.S. Abel and J.W. Chaffee".

7521: 5870: 5362: 3853:

The receiver uses messages received from satellites to determine the satellite positions and time sent. The

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satellite, which proved the feasibility of placing accurate clocks in space, a technology required for GPS.

18111: 17579: 15718: 15503: 15423: 15363: 14476: 14456: 14299: 13402: 12468: 9628:

Bury, Grzegorz; Sośnica, Krzysztof; Zajdel, Radosław; Strugarek, Dariusz; Hugentobler, Urs (January 2021).

6827: 5445:

to enhance GPS's accuracy in Asia-Oceania, with satellite navigation independent of GPS scheduled for 2023.

3837: 3184: 3170: 2963: 2097: 1948: 300: 12164:"Challenges related to the determination of altitudes of mountain peaks presented on cartographic sources" 8980:"Geocenter coordinates derived from multi-GNSS: a look into the role of solar radiation pressure modeling" 3352:

to navigate and perform maneuvers in the war. The war also demonstrated the vulnerability of GPS to being

2652:

to the frequencies transmitted by the satellites, receiver-processors, and a highly stable clock (often a

2636: 18429: 18335: 17934: 16569: 16497: 15997: 15572: 15539: 14802: 14694: 14241: 13682: 11063: 9979:

Dennis D. McCrady (August 1994). The GPS Burst Detector W-Sensor (Report). Sandia National Laboratories.

9714:"Estimating global geodetic parameters using SLR observations to Galileo, GLONASS, BeiDou, GPS, and QZSS" 9323:

Yang, Zhuo; Franz, Mark L.; Zhu, Shanjiang; Mahmoudi, Jina; Nasri, Arefeh; Zhang, Lei (January 1, 2018).

8500: 7396: 6005: 5789: 4800: 4781:, and signals from at minimum four satellites are needed. In that case each of the equations describes a 4678:. The locus of points having a constant difference in distance to two points (here, two satellites) is a 2116: 1215: 1101: 798: 778: 38: 14007: 11530:. National Coordination Office for Space-Based Positioning, Navigation, and Timing (PNT). October 2001. 10573: 10361: 8157: 3319:

or about 118 km/s (260,000 mph/s) have been developed for use in 155-millimeter (6.1 in)

18646: 18407: 18274: 18209: 17968: 17902: 16099: 16061: 15964: 15554: 15418: 15383: 15346: 15158: 15001: 14958: 14491: 14461: 8939:"System-specific systematic errors in earth rotation parameters derived from GPS, GLONASS, and Galileo" 7323: 5543: 5102: 3394: 3081:: GPS enables highly accurate timestamping of power system measurements, making it possible to compute 2916: 2524: 2516: 2249: 2201: 1883: 1742:

In 1996, recognizing the importance of GPS to civilian users as well as military users, U.S. President

1679: 989: 939: 915: 11415:

Sirola, Niilo (March 2010). "Closed-form algorithms in mobile positioning: Myths and misconceptions".

11317:

Grafarend, Erik W. (2002). "GPS Solutions: Closed Forms, Critical and Special Configurations of P4P".

10567:"Interface Specification IS-GPS-200, Revision D: Navstar GPS Space Segment/Navigation User Interfaces" 9960: 9324: 9267: 6963: 6853: 5904:

National Coordination Office for Space-Based Positioning, Navigation, and Timing (February 22, 2021).

5798: 3880: 16443: 16353: 16296: 16076: 16066: 15870: 15639: 15133: 14939: 14042: 13971: 12574: 12203: 11723: 10975: 8133: 6549: 5834: 5495: 5379: 4683: 3426: 3406: 3349: 3306: 3297:

Missile and projectile guidance: GPS allows accurate targeting of various military weapons including

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missile, which required them to know the submarine's location.) This led them and APL to develop the

1008: 931: 923: 762: 80: 12505: 11932: 11914: 11849: 11787: 11615: 11425: 8204: 3332:

GPS satellites carry a set of nuclear detonation detectors consisting of an optical sensor called a

817:(SA), a deliberate error introduced into the GPS data (which military receivers could correct for). 18597: 18492: 16916: 16301: 15858: 15351: 14792: 13920: 13541: 13287: 11036: 10730: 9712:

Sośnica, K.; Bury, G.; Zajdel, R.; Strugarek, D.; Drożdżewski, M.; Kazmierski, K. (December 2019).

8402: 7643: 5505: 5432:

and other partner countries, began operation in 2016, and is expected to be fully deployed by 2020.

5391: 5195:

possibly duplicate references to the same phase stuff, esp. between RTK and carrier-phase tracking.

5132: 3825: 3447: 2700:

protocols. Receivers can interface with other devices using methods including a serial connection,

2432: 1675: 1330: 1131:

Updates from the Navy TRANSIT system were too slow for the high speeds of Air Force operation. The

985: 874: 758: 460: 407: 309: 217: 18422: 18417: 12740: 12632: 5967:

National Coordination Office for Space-Based Positioning, Navigation, and Timing (March 3, 2022).

1195:

The effect of the ionosphere on radio transmission was investigated in a geophysics laboratory of

992:(APL) decided to monitor its radio transmissions. Within hours they realized that, because of the 18487: 17929: 17743: 16662: 16448: 15947: 15838: 15790: 15689: 15143: 15138: 15006: 14981: 14724: 14292: 14038: 13490: 12461: 9128:

Wesche, Christine; Eisen, Olaf; Oerter, Hans; Schulte, Daniel; Steinhage, Daniel (January 2007).

8726:

Sośnica, Krzysztof; Thaller, Daniela; Dach, Rolf; Jäggi, Adrian; Beutler, Gerhard (August 2013).

7985:

Georg zur Bonsen; Daniel Ammann; Michael Ammann; Etienne Favey; Pascal Flammant (April 1, 2005).

7621: 4687: 3560: 3124: 3082: 3078: 2973: 2732: 2456: 2276: 2006: 1824: 1736: 1078: 1040: 598: 558: 316: 12306: 10816: 10544: 9239:

Nakajima, Yuu; Shiina, Hironori; Yamane, Shohei; Ishida, Toru; Yamaki, Hirofumi (January 2007).

8658: 6523: 3340:. General William Shelton has stated that future satellites may drop this feature to save money. 2219:

GPS requires four or more satellites to be visible for accurate navigation. The solution of the

2176:

The description above is representative of a receiver start-up situation. Most receivers have a

30:

This article is about the American global navigation satellite system. For similar systems, see

18547: 17549: 15589: 15438: 15378: 15356: 15028: 14890: 14839: 14812: 14231: 14128: 13606: 12497: 12453: 11420: 10637:

The Telecommunications Handbook: Engineering Guidelines for Fixed, Mobile and Satellite Systems

5465: 5124:

quantities. When there are two (usually the case), only one is a near-Earth sensible solution.

3877: ≥ 4. When the time of message reception indicated by the on-board receiver clock is 2823:

for position reporting; is often critical during emergency and disaster communications support.

2339: 2069: 1868: 1762: 1626: 1247: 1208: 1123: 958: 859: 578: 11755: 11155: 11116: 10591: 6115: 2656:). They may also include a display for providing location and speed information to the user. 18694: 18116: 17992: 17955: 17895: 17839: 17016: 16986: 16931: 16363: 15930: 15795: 15767: 15735: 15513: 14996: 14915: 14747: 14466: 14133: 14077: 14067: 14057: 12180: 12163: 11886:"Federal Communications Commission Fixed and Mobile Services in the Mobile Satellite Service" 11197: 10144: 8289: 7961: 7416: 5515: 5294:

In January 2011, the FCC conditionally authorized LightSquared's wholesale customers—such as

4562: 3001: 2912: 2890: 2844: 2623: 1864: 1648: 1284: 1204: 965: 721: 638: 388: 283: 12859: 11698: 11640: 10695:

Borre, Kai; M. Akos, Dennis; Bertelsen, Nicolaj; Rinder, Peter; Jensen, Søren Holdt (2007).

10058:"GPS jamming is a growing threat to satellite navigation, positioning, and precision timing" 9729: 9130:"Surface topography and ice flow in the vicinity of the EDML deep-drilling site, Antarctica" 8937:

Zajdel, Radosław; Sośnica, Krzysztof; Bury, Grzegorz; Dach, Rolf; Prange, Lars (July 2020).

6405: 1663:

By 1985, ten more experimental Block-I satellites had been launched to validate the concept.

858:

satellites and Next Generation Operational Control System (OCX) which was authorized by the

18190: 18043: 16502: 16406: 15711: 15584: 15577: 15185: 15013: 14885: 14284: 14123: 14062: 13907: 13889: 13695: 13498: 13268: 12488: 11368: 11326: 11283: 11238:

Principles of GNSS, Inertial, and Multisensor Integrated Navigation Systems, Second Edition

10434: 9725: 9678: 9641: 9600: 9559: 9518: 9471: 9434: 9336: 9289: 9203: 9141: 9032: 8991: 8950: 8901: 8804: 8742: 7880: 7839: 7498: 7267: 7227: 5835:"Global Positioning System Standard Positioning Service Performance Standard - 4th Edition" 5593: 5470: 5357: 5246: 4743: 3722: 2701: 2335: 1223: 1094: 766: 538: 488: 414: 42: 31: 12329: 9192:"A review of travel behavioural pattern using GPS dataset: A systematic literature review" 8727: 8530: 8101:

Daly, P. (December 1993). "Navstar GPS and GLONASS: global satellite navigation systems".

8007: 7784: 6797: 6425: 2804:

is mounted on the roof of a hut containing a scientific experiment needing precise timing.

8: 18470: 18084: 16911: 16261: 16049: 15925: 15270: 15116: 14950: 14920: 14849: 14332: 13881: 13861: 13841: 13831: 13803: 13793: 13788: 13581: 13338: 13328: 10953: 9268:"Estimating wildfire evacuation decision and departure timing using large-scale GPS data" 7344: 5878: 5866: 5326: 5128: 3733:

The L4 band at 1.379913 GHz is being studied for additional ionospheric correction.

3377: 3108: 2852: 2781: 1936: 1652: 1227: 1029: 450: 398: 17: 11372: 11330: 11287: 10438: 10397: 9682: 9645: 9604: 9563: 9522: 9475: 9438: 9340: 9293: 9207: 9145: 9036: 8995: 8954: 8905: 8808: 8746: 7984: 7884: 7753: 5968: 3762:

Please help update this article to reflect recent events or newly available information.

2610:

According to the Government Accounting Office in 2019, the 2021 deadline looked shaky.

2138:, which is essentially mean sea level. These coordinates may be displayed, such as on a 1295:

use of GPS and its augmentations without unduly disrupting or degrading civilian uses".

18664: 18412: 18330: 18325: 18169: 18147: 18028: 17978: 17521: 17006: 16894: 16358: 16231: 15777: 14567: 14446: 14441: 13961: 13826: 13798: 13773: 13768: 13763: 13428: 12185: 11527: 11384: 11342: 11299: 10465: 10422: 9694: 9487: 9398: 9371: 9279: 9174: 9048: 8758: 8708: 8335: 8315: 8176: 6779: 6322: 5557: 5520: 5510: 5367: 5315: 3453: 3044: 3039:

determination of low-orbiting satellites with GPS receiver installed on board, such as

2995:

data) and other documents for purposes such as creating map overlays with devices like

2882: 2653: 2547:). These updates synchronize the atomic clocks on board the satellites to within a few 2396: 2139: 1924: 1147: 969: 935: 370: 340: 322:

runs through a checklist during Global Positioning System satellite operations in 2004.

181: 11006: 10783:"United Launch Alliance Successfully Launches GPS IIF-12 Satellite for U.S. Air Force" 9241:"Disaster Evacuation Guide: Using a Massively Multiagent Server and GPS Mobile Phones" 2873:: applying location and routes for cars and trucks to function without a human driver. 2395:

The space segment (SS) is composed of 24 to 32 satellites, or Space Vehicles (SV), in

18511: 18282: 18038: 17963: 17574: 16071: 15942: 15403: 15106: 14623: 14613: 14486: 14431: 14426: 13981: 13966: 13897: 13758: 13348: 12554: 12422: 12376: 12355: 12189: 11461: 11346: 11242: 11203: 11161: 11122: 10842:"The System: Test Data Predicts Disastrous GPS Jamming by FCC-Authorized Broadcaster" 10702: 10668: 10641: 10597: 10470: 10452: 10305: 9980: 9698: 9491: 9403: 9352: 9305: 9221: 9157: 9108: 9067: 9052: 8919: 8293: 7965: 7936: 7896: 7189: 7155: 7040: 6771: 6724: 6682: 6253: 6181: 6147: 5799:"Global Positioning System Wide Area Augmentation System (WAAS) Performance Standard" 5334: 5299: 5262:. On March 1, 2001, the FCC received an application from LightSquared's predecessor, 5229: 3737: 3643:

Coarse-acquisition (C/A) and encrypted precision (P(Y)) codes, plus the L1 civilian (

3064: 2943: 2926: 2870: 2864: 2860: 2856: 2775: 2605:

Supports higher volume near real-time command and control capabilities and abilities.

1655:

because of navigational errors, killing all 269 people on board, U.S. President

1043:

of five satellites and could provide a navigational fix approximately once per hour.

470: 455: 11493:

Oszczak, B., "New Algorithm for GNSS Positioning Using System of Linear Equations",

11388: 11303: 8762: 8712: 8655:"Publications and Standards from the National Marine Electronics Association (NMEA)" 8339: 8260: 1003: 18614: 18445: 18313: 18121: 18064: 18033: 17973: 17569: 17534: 17434: 16383: 15458: 15285: 15240: 15220: 14834: 14638: 14603: 14598: 14552: 14537: 14511: 14506: 14143: 12175: 11453: 11430: 11376: 11334: 11291: 10957: 10923: 10460: 10442: 10263: 9733: 9686: 9649: 9608: 9567: 9526: 9479: 9442: 9393: 9383: 9348: 9344: 9297: 9248: 9211: 9177:

Proceedings of the 8th International Workshop on Information Integration on the Web

9149: 9100: 9040: 8999: 8958: 8909: 8812: 8750: 8698: 8690: 8327: 8110: 7928: 7888: 7262: 7222: 7092: 6763: 5569: 5375: 5272: 5218: 5169: 4727: 4695: 3169:: GPS technology integrated with computers and mobile communications technology in 3120: 2977: 2536: 2508: 2323: 2319: 1961: 1835: 1259: 1255: 1116:) and so the need to fix the launch position had similarity to the SLBM situation. 1090: 1082: 950: 825: 714: 465: 9630:"Determination of precise Galileo orbits using combined GNSS and SLR observations" 7417:"National Executive Committee for Space-Based Positioning, Navigation, and Timing" 7297: 6783: 4573:

done by multiplying the basic resolution of the receiver by quantities called the

3703:

Used as a civilian safety-of-life (SoL) signal on Block IIF and newer satellites.

3577:– the precise orbit for the satellite. The fourth and fifth subframes contain the 3541:

on L1 (C/A and P/Y) and L2 (P/Y) frequencies at a rate of 50 bits per second (see

3145:: surveyors use absolute locations to make maps and determine property boundaries. 2419:(angle along the equator from a reference point to the orbit's intersection). The 1207:

at AFGRL in 1974. She was concerned with the curving of the paths of radio waves (

18450: 18377: 16431: 16084: 15853: 15843: 15654: 15373: 15170: 14824: 14663: 14608: 13642: 13627: 13576: 12370: 12349: 12085: 12065: 11920: 11514: 11236: 10982: 10871: 10696: 10662: 10635: 9967: 9846: 9216: 9191: 8437: 8351: 8283: 8183: 8164: 7955: 7403: 7351: 7183: 7149: 7021: 6943: 6718: 6141: 5383: 5371: 5127:

When a receiver uses more than four satellites for a solution, Bancroft uses the

4691: 4581: 3361: 3310: 3238: 3156: 2981: 2922: 2886: 2801: 2504: 2412: 2322:

develops, maintains, and operates the space and control segments. GPS satellites

2177: 2161: 1954: 1944: 1721: 1711: 1496: 1271:

to meet the growing needs of the military, civilians, and the commercial market.

1012: 927: 919: 10325: 10259:"Russian forces have hit on a cheap way to foil US precision weapons in Ukraine" 9546:

Zajdel, R.; Sośnica, K.; Dach, R.; Bury, G.; Prange, L.; Jäggi, A. (June 2019).

8344: 7814: 6673: 5600: 4746:

are centered at the GPS satellites, whose radii equal the measured pseudoranges

3598:

All satellites broadcast at the same frequencies, encoding signals using unique

1203:

corrections to GPS location. Of note is work done by Australian space scientist

18159: 17096: 16552: 16512: 15664: 15632: 15619: 15466: 15265: 14732: 14720: 14643: 13818: 13647: 13637: 13237: 13056: 9654: 9629: 9548:"Network Effects and Handling of the Geocenter Motion in Multi-GNSS Processing" 9447: 9422: 9240: 9153: 9004: 8979: 8963: 8938: 8914: 8889: 8475: 7871:

Abel, J.S.; Chaffee, J.W. (1991). "Existence and uniqueness of GPS solutions".

7446: 6767: 5429: 5387: 4600: 4036: 3302: 3290:

to allow them to engage targets accurately. Military aircraft, particularly in

3280: 3234: 3160: 3139:: used in football and rugby for the control and analysis of the training load. 2949: 2929:: many emergency services depend upon GPS for location and timing capabilities. 2544: 2520: 2499:(SCN) ground antennas (for additional command and control capability) and NGA ( 2420: 2245: 2142:, or recorded or used by some other system, such as a vehicle guidance system. 2109: 2058: 1860: 1810: 1785: 1707: 1692:

from 1990 to 1991 was the first conflict in which the military widely used GPS.

1571: 1546: 1268: 1235: 1109: 1025: 993: 829: 678: 445: 419: 12392: 11457: 11434: 9738: 9713: 9613: 9588: 9483: 9301: 9044: 8817: 8792: 8754: 8679: 8331: 8226: 7700: 18719: 18152: 18069: 16994: 16174: 15865: 15493: 15393: 15338: 15153: 15073: 14870: 14760: 14742: 14668: 14658: 14593: 14562: 14527: 14381: 13433: 12985: 12912: 11450:

GNSS Positioning Approaches – GPS Satellite Surveying, Fourth Edition – Leick

11401:

Chaffee, J. and Abel, J., "On the Exact Solutions of Pseudorange Equations",

11380: 10456: 9356: 9309: 9225: 9161: 8923: 7940: 7900: 6775: 6611: 6257: 4807: 4630:

the satellites. The receiver is then located at one of the two intersections.

4610: 4222:{\displaystyle d_{i}=\left({\tilde {t}}_{i}-b-s_{i}\right)c,\;i=1,2,\dots ,n} 3802:

Demodulating and Decoding GPS Satellite Signals using the Coarse/Acquisition

3786: 3644: 3353: 3291: 3223: 3024: 2953: 2902: 2812: 2683:

Many GPS receivers can relay position data to a PC or other device using the

2560: 2556: 2378: 2365: 2225: 2193: 2049: 1800: 1656: 1521: 1471: 1446: 1239: 1164: 1070: 984:) in 1957, two American physicists, William Guier and George Weiffenbach, at 855: 805:

announced that the GPS system would be made available for civilian use as of

802: 774: 319: 10813:"Air Force Successfully Transmits an L5 Signal From GPS IIR-20(M) Satellite" 9839: 8836: 8544: 8114: 7644:"President announces Roger Easton recipient of National Medal of Technology" 6902: 6497: 6467: 3112: 2796: 2229: 1820:

issued a report warning that some GPS satellites could fail as soon as 2010.

901:

Air Force film introducing the Navstar Global Positioning System, circa 1977

18587: 18142: 18074: 17918: 17859: 16864: 16226: 16126: 16044: 15549: 15453: 15180: 15175: 15165: 15023: 14816: 14684: 14577: 14496: 14416: 14411: 14093: 14072: 13601: 13459: 12368: 11363:

Bancroft, S. (January 1985). "An Algebraic Solution of the GPS Equations".

10474: 9407: 6278: 5768: 5605: 5490: 5259: 3780: 3210: 2659:

GPS receivers may include an input for differential corrections, using the

2540: 2512: 2448: 2444: 2424: 2416: 2189: 2085: 1932: 1902: 1890: 1796: 1743: 1710:, which originally managed the system, was inactivated and replaced by the 1647:

In 1983, after Soviet interceptor aircraft shot down the civilian airliner

1421: 1334: 1251: 1140: 1113: 837: 806: 403: 209: 10513: 10232:"Evidence shows Iran shot down Ukrainian plane 'intentionally' | AvaToday" 9252: 9104: 8630:"Next-gen GPS ground system expected to come online this summer: Calvelli" 8529:. Air Force Space Command News Service. September 14, 2011. Archived from 8430: 7584:"Air Force GPS Problem: Glitch Shows How Much U.S. Military Relies On GPS" 7371: 6440: 6363: 6214: 2991:: applies location coordinates to digital objects such as photographs (in 2527:

25 km (16 mi) ESE of Colorado Springs, which is operated by the

1666:

Beginning in 1988, command and control of these satellites was moved from

17564: 17559: 17554: 17499: 17444: 17149: 16921: 15848: 15627: 15594: 15443: 15315: 15275: 15046: 15041: 15018: 14875: 14829: 14797: 14633: 14628: 14572: 14037: 13742: 13690: 12103: 10753:"First Block 2F GPS Satellite Launched, Needed to Prevent System Failure" 10303: 9690: 9572: 9547: 9423:"Evolution of orbit and clock quality for real-time multi-GNSS solutions" 8694: 7026: 5627: 5581: 5475: 4769: 4374:{\displaystyle d_{i}={\sqrt {(x-x_{i})^{2}+(y-y_{i})^{2}+(z-z_{i})^{2}}}} 3843: 3717: 3565: 3470: 3422: 3402: 3365: 3259:

Frequency-Hopping Radio Clock Coordination: Military radio systems using

3152: 3100: 2952:: used to identify, locate and maintain contact reports with one or more 2876: 2830: 2555:

of each satellite's internal orbital model. The updates are created by a

2404: 2241: 2157: 1928: 1667: 1396: 1267:

ongoing initiative by the U.S. Department of Defense through a series of

1189: 943: 770: 360: 13323: 10698:

A Software-Defined GPS and Galileo Receiver. A single-Frequency Approach

10447: 10202:"Iran Spokesman Confirms Mysterious Disruption Of GPS Signals In Tehran" 9421:

Kazmierski, Kamil; Zajdel, Radoslaw; Sośnica, Krzysztof (October 2020).

8364: 7879:(6). Institute of Electrical and Electronics Engineers (IEEE): 952–956. 4625: 3230: 2126:

The receiver's Earth-centered solution location is usually converted to

276: 18475: 18340: 18320: 18079: 17256: 17069: 16485: 16463: 16209: 15310: 15305: 14934: 14844: 14777: 14772: 14737: 14532: 13711: 13632: 13566: 11338: 9985: 9809: 9531: 9506: 8703: 5419:

began global services in 2018 and finished its full deployment in 2020.

3421:

GPS time is theoretically accurate to about 14 nanoseconds, due to the

3333: 3268: 3166: 3159:

motion and deformation to estimate seismic strain buildup for creating

3104: 3096: 3092: 3088: 3068: 3056: 3030: 2996: 2988: 2933: 2848: 2834: 2826: 2746: in this section. Unsourced material may be challenged and removed. 2548: 2290: in this section. Unsourced material may be challenged and removed. 2089: 2054: 2020: in this section. Unsourced material may be challenged and removed. 1685:

On February 14, 1989, the first modern Block-II satellite was launched.

1219: 1200: 1168: 12108: 9189: 8791:

Bury, Grzegorz; Sośnica, Krzysztof; Zajdel, Radosław (December 2019).

7987:"Continuous Navigation Combining GPS with Sensor-Based Dead Reckoning" 7723:"Mathematician inducted into Space and Missiles Pioneers Hall of Fame" 7014: 5236: 3736:

The L5 frequency band at 1.17645 GHz was added in the process of

2467: 1813:

Control System was transferred to the new Architecture Evolution Plan.

18480: 18048: 18005: 17159: 17111: 16879: 15483: 14787: 14782: 14138: 14118: 14108: 13986: 13668: 12748: 12543: 11295: 11195: 9018: 8978:

Zajdel, Radosław; Sośnica, Krzysztof; Bury, Grzegorz (January 2021).

7932: 7927:(4). Institute of Electrical and Electronics Engineers (IEEE): 1163. 7892: 6283:. Astronautica Acta II (in German) (25). Retrieved October 19, 2014. 5155: 4782: 4778: 4679: 3814: 3803: 3573: 3148: 3142: 2937: 2840: 2705: 2684: 2640:

The first portable GPS survey unit, a Leica WM 101, displayed at the

2552: 2532: 2344: 2131: 2073: 2065: 1847: 1323: 1066: 981: 439: 365: 11274:

Hoshen J (1996). "The GPS Equations and the Problem of Apollonius".

10593:

Satellite Systems for Personal Applications: Concepts and Technology

10488: 9325:"Analysis of Washington, DC taxi demand using GPS and land-use data" 8577:"Raytheon's $ 7 Billion GPS Stations Are Running 73% Over Estimates" 8451:"DoD Decision Breathes New Life into Critical OCX Satellite Program" 4742:). The insphere location is such that it touches other spheres. The 4706: 2815:: clock synchronization required for several digital modes such as 2721: 2566:

When a satellite's orbit is being adjusted, the satellite is marked

2265: 1995: 801:

was shot down when it mistakenly entered Soviet airspace, President

18582: 18455: 18345: 14471: 14113: 14103: 14098: 13851: 13750: 13700: 13663: 13591: 13586: 13333: 12549: 12538: 12533: 12528: 12523: 12518: 12513: 10001:"US Air Force Eyes Changes To National Security Satellite Programs" 9284: 9021:"A consistent combination of GNSS and SLR with minimum constraints" 7954:

Grewal, Mohinder S.; Weill, Lawrence R.; Andrews, Angus P. (2007).

7218:"Navstar - Global system will provide accurate data for navigation" 5905: 5829: 5295: 5255: 3810: 3345: 3320: 3313:. Embedded GPS receivers able to withstand accelerations of 12,000 3264: 3130: 3127:

and microwave observations for deriving global geodetic parameters.

3060: 3018: 2969: 2697: 2645: 2127: 1792: 1747: 1689: 1644:

In 1978, the first experimental Block-I GPS satellite was launched.

1319: 1231: 1136: 1063: 1047: 997: 905: 821: 618: 435: 424: 57: 13622: 13366: 11641:"Federal Communications Commission Table of Frequency Allocations" 11614:. Federal Communications Commission. April 6, 2011. Archived from 10235: 9388: 8604:"Space Force sees further delays to 'troubled' GPS ground segment" 7614:"Contract Award for Next Generation GPS Control Segment Announced" 6990:"National Positioning, Navigation and Timing Advisory Board Named" 4239:

is the geometric distance or range between receiver and satellite

3730:

space. One usage is the enforcement of nuclear test ban treaties.

1716: 1093:

posture, accurate determination of the SLBM launch position was a

1011:’s managers for the Timation program and, later, the GPS program: 840:

signed a bill ordering that Selective Availability be disabled on

270:

Artist's impression of GPS Block IIR satellite in Earth orbit

18592: 18465: 18367: 18362: 18195: 18164: 18137: 17657: 17652: 17204: 16677: 14880: 14764: 14648: 14501: 14256: 14251: 14216: 14194: 13925: 13885: 13516: 13443: 13297: 13018: 13013: 13008: 13003: 12998: 12993: 12975: 12970: 12965: 12960: 12955: 12950: 12945: 12940: 12935: 12930: 12925: 12920: 12902: 12897: 12892: 12887: 12882: 12877: 12872: 12867: 12849: 12844: 12839: 12834: 12829: 12824: 12819: 12814: 12809: 12804: 12799: 12794: 12789: 12784: 12779: 12774: 12769: 12764: 12759: 12754: 12730: 12725: 12720: 12715: 12710: 12450:– General public education website created by the U.S. Government 8079: 7181: 6716: 5485: 5407: 5303: 5263: 4604:

2-D Cartesian true-range multilateration (trilateration) scenario

3542: 3315: 3195:

balloon launches that regularly reach 30 km (100,000 feet).

3052: 3048: 2959: 2906: 2471:

Ground monitor station used from 1984 to 2007, on display at the

2408: 2352: 2197: 1834:

On February 25, 2010, the U.S. Air Force awarded the contract to

1767: 1758: 1619: 498: 355: 332: 12483: 12419:

Pinpoint: How GPS is Changing Technology, Culture, and Our Minds

10664:

Global Positioning System. Signals, Measurements and Performance

9020: 7957:

Global Positioning Systems, Inertial Navigation, and Integration

6096:. National Institute of Standards and Technology. March 17, 2021 5639:

Orbital periods and speeds are calculated using the relations 4π

2628: 294: 18460: 18372: 18357: 18352: 17887: 16830: 15300: 15190: 14547: 14542: 14451: 14436: 14361: 14210: 13915: 13846: 13836: 13506: 13282: 12705: 12700: 12695: 12690: 12685: 12680: 12675: 12670: 12665: 12660: 12655: 12650: 12645: 12640: 12622: 12617: 12612: 12607: 12602: 12597: 12592: 12587: 12582: 12564: 12160: 11675:. Federal Communications Commission. March 1, 2001. p. 9. 10572:. Navstar GPS Joint Program Office. p. 103. Archived from 10089:"GPS Under Attack as Crooks, Rogue Workers Wage Electronic War" 9586: 8189: 7670:"Inducted Technologies / 1998: Global Positioning System (GPS)" 6835: 6546:"A Guide to the Global Positioning System (GPS) – GPS Timeline" 6029:"GPS will be accurate within one foot in some phones next year" 4578: 3072: 2898: 2879:: both civilian and military cartographers use GPS extensively. 2664: 2192:

of position measurement. GPS units can use measurements of the

1700: 980:

When the Soviet Union launched its first artificial satellite (

608: 568: 506: 12059:"Spokesperson Statement on NTIA Letter – LightSquared and GPS" 10924:"GPS Almanacs, NANUS, and Ops Advisories (including archives)" 8793:"Multi-GNSS orbit determination using satellite laser ranging" 8527:"GPS Completes Next Generation Operational Control System PDR" 7185:

The Precision Revolution: GPS and the Future of Aerial Warfare

6720:

The Precision Revolution: GPS and the Future of Aerial Warfare

6681:. Washington, DC: US Government Printing Office. p. 331. 3798: 17539: 16276: 14421: 13778: 13448: 12559: 12261:"Japan Prepares for GPS Failure with Quasi-Zenith Satellites" 11993:"FCC Chairman Genachowski Letter to Senator Charles Grassley" 10326:"The Role of GPS in Precise Time and Frequency Dissemination" 9245:

2007 International Symposium on Applications and the Internet

8318:(2007). "Finding the repeat times of the GPS constellation". 6349:

Where good ideas come from, the natural history of innovation

6173: 5530: 5395: 5338: 4726:

The receiver position can be interpreted as the center of an

3370: 3136: 3036: 2455:

As of February 2019, there are 31 satellites in the GPS

2135: 1151: 1033: 954: 841: 393: 14314: 8177:

What the Global Positioning System Tells Us about Relativity

7754:"Queen Elizabeth Prize for Engineering: GPS pioneers lauded" 7147: 6876:"United States Updates Global Positioning System Technology" 5241:

In the United States, GPS receivers are regulated under the

3664:

and military codes on the Block IIR-M and newer satellites.

3647:) and military (M) codes on Block III and newer satellites. 3329:

Reconnaissance: Patrol movement can be managed more closely.

2784:, meaning it has significant civilian applications as well. 17544: 13991: 13976: 13871: 13866: 13808: 12328:. United States Coast Guard. September 1996. Archived from 10723:"United States Nuclear Detonation Detection System (USNDS)" 10694: 10396:, El Segundo, CA: The Aerospace Corporation, archived from 10323: 9784:"The Use of GPS Tracking Technology in Australian Football" 9504: 8476:"GPS.gov: Next Generation Operational Control System (OCX)" 8427: 6852:. International Civil Aviation Organization. Archived from 4566: 3298: 3040: 2992: 2693: 2689: 2660: 1288: 848: 844: 810: 695: 588: 14980: 14624:

AGM-84H/K Standoff Land Attack Missile - Expanded Response

12391: 12204:"China launches final satellite in GPS-like Beidou system" 11925: 11908: 10387:

Fliegel, Henry F.; DiEsposti, Raymond S. (December 1996),

9711: 9627: 9238: 7345:

The Global Positioning System: Assessing National Policies

7067:"Recap story: Three Atlas 5 launch successes in one month" 5346:

National Telecommunications and Information Administration

4456:{\displaystyle p_{i}=\left({\tilde {t}}_{i}-s_{i}\right)c} 2855:

and precise orbit determination. GPS is also used in both

949:

The design of GPS is based partly on similar ground-based

264: 18308: 14865: 13996: 13856: 13783: 12410: 11936: 11528:"Frequently Asked Questions About Selective Availability" 9272:

Transportation Research Part D: Transport and Environment

9265: 8657:. National Marine Electronics Association. Archived from 8392:"Optimizing performance through constellation management" 6361: 5865: 5225:

in general, a network of satellites used for navigation.

5120:

situations, compared to iterative least squares methods.

3661: 3457: 2816: 2780:

While originally a military project, GPS is considered a

1872: 1039:

TRANSIT was first successfully tested in 1960. It used a

12369:

Jaizki Mendizabal; Roc Berenguer; Juan Melendez (2009).

11646:. Federal Communications Commission. November 18, 2011. 11508:

Vehicles that use GPS jammers are big threat to aircraft

11480:

Alfred Kleusberg, "Analytical GPS Navigation Solution",

11417:

7th Workshop on Positioning Navigation and Communication

10590:

Richharia, Madhavendra; Westbrook, Leslie David (2011).

9127: 6177:

Handbook of Space Engineering, Archaeology, and Heritage

4035:

is the satellite time. Assuming the message traveled at

2115:

In practice the receiver position (in three dimensional

135: 124: 12447: 11114: 11033:"Geometric Dilution of Precision (GDOP) and Visibility" 9776: 9420: 8890:"Sub-daily polar motion from GPS, GLONASS, and Galileo" 8725: 8313: 7497:. losangeles.af.mil. September 17, 2007. Archived from 6060:"Superaccurate GPS Chips Coming to Smartphones in 2018" 4638:

and the pseudorange between the receiver and satellite

3564:

50-bit/s, this gives 750 seconds to transmit an entire

12354:. American Institute of Aeronautics and Astronautics. 11701:. Federal Communications Commission. September 4, 2003 11160:. Springer Science & Business Media. p. 338. 10970: 10968: 10304:

David W. Allan; Neil Ashby; Clifford C. Hodge (1997).

6246:"Gladys West: the hidden figure who helped invent GPS" 4662:) cancels out, resulting in a difference of distances 4634:

If the pseudorange between the receiver and satellite

4104:{\displaystyle \left({\tilde {t}}_{i}-b-s_{i}\right)c} 3397:(UTC), the atomic clocks on the satellites are set to 2559:

that uses inputs from the ground monitoring stations,

250: 12099:"Russia Launches Three More GLONASS-M Space Vehicles" 11718: 11716: 11403: