The Global Positioning System ( GPS ) is a space-based satellite navigation system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites.

GPS was created and realized by the U. S. Department of Defense ( DoD ) and was originally run with 24 satellites.

Advances in technology and new demands on the existing system have now led to efforts to modernize the GPS system and implement the next generation of GPS III satellites and Next Generation Operational Control System ( OCX ).

( To achieve accuracy requirements, GPS uses principles of general relativity to correct the satellites ' atomic clocks.

With the individual satellites being 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, Navstar-GPS, which was later shortened simply to GPS.

It is only because GPS satellites orbit about the geocentre, that this point becomes naturally the origin of a coordinate system defined by satellite geodetic means, as the satellite positions in space are themselves computed in such a system.

The known points used for point positioning can be triangulation points of a higher order network, or GPS satellites.

The BBC understands € 500 million (£ 440M ) will become available to make the extra purchase, taking Europe's version of GPS from 18 operational satellites in the next few years to 24.

Though Selective Availability capability still exists, on 19 September 2007 the US Department of Defense announced that newer GPS satellites would not be capable of implementing Selective Availability ;

the wave of Block IIF satellites launched in 2009, and all subsequent GPS satellites, do not support SA.

As old satellites are replaced in the GPS Block IIIA program, SA will cease to be an option.

Relativistic effects cease to be negligible when near very massive bodies ( as with the precession of Mercury's orbit about the Sun ), or when extreme precision is needed ( as with calculations of the orbital elements and time signal references for GPS satellites.

An animation depicting the orbits of GPS satellites in medium Earth orbit.

Timekeeping technologies such as the GPS satellites and Network time protocol ( NTP ) provide real-time access to a close approximation to the UTC timescale, and are used for many terrestrial synchronization applications.

The sextant is not dependent upon electricity ( unlike many forms of modern navigation ) or anything human-controlled ( like GPS satellites ).

A GPS receiver functions by precisely measuring the transit time of signals received from several satellites.

GPS is a receive-only system that uses relative timing measurements from several satellites ( and the known positions of the satellites ) to determine receiver position.

Hence, it is computed from observations of distant quasars using long baseline interferometry, laser ranging of the Moon and artificial satellites, as well as the determination of GPS satellite orbits.

It is more reliable, and often more accurate, than a GPS receiver for measuring altitude ; GPS altimeters may be unavailable, for example, when one is deep in a canyon, or may give wildly inaccurate altitudes when all available satellites are near the horizon.

* Research from the University of Southern California reports that in 2007, humankind successfully sent 1. 9 zettabytes of information through broadcast technology such as televisions and GPS.

WGS 84 is used by DoD for all its mapping, charting, surveying, and navigation needs, including its GPS " broadcast " and " precise " orbits.

It was used as the reference frame for broadcast GPS Ephemerides ( orbits ) beginning January 23, 1987.

( See John Harrison ) Today, time is measured with a chronometer, a quartz watch, a shortwave radio time signal broadcast from an atomic clock, or the time displayed on a GPS.

Other examples of wireless technology include GPS units, garage door openers, wireless computer mice, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones.

However the low cost of ADF and RDF systems, and the continued existence of AM broadcast stations ( as well as navigational beacons in countries outside North America ) has allowed these devices to continue to function, primarily for use in small boats, as an adjunct or backup to GPS.

Personal two-way radios are also sometimes combined with other electronic devices ; Garmin's Rino series combine a GPS receiver in the same package as an FRS / GMRS walkie-talkie ( allowing Rino users to transmit digital location data to each other ) Some personal radios also include receivers for AM and FM broadcast radio and, where applicable, NOAA Weather Radio and similar systems broadcasting on the same frequencies.

He recovers Henry Gupta's GPS scrambler which was used to lure the British Navy into Chinese waters to try and spark an international incident ss the existing Chinese government being not receptive to giving Carver Media Group Network exclusive broadcast rights in China, Carver plans to start a war to eliminate the government in favor of politicians more supportive to his plans.

The SUNA broadcast service is fully compliant with both the RDS and TMC standard however the broadcast is encrypted and therefore will not work on all in-car GPS navigation systems that do not have a commercial arrangement with SUNA.

EPN data are raw GPS / GLONASS pseudorange and phase observations, broadcast ephemerides, and supporting types of raw data ( such as meteorological ) as they are gathered by the Tracking Stations.

The master clock in a clock network can receive accurate time in a number of ways: through the United States GPS satellite constellation, a Network Time Protocol server, the CDMA cellular phone network, a modem connection to a time source, or by listening to radio transmissions from WWV or WWVH, or a special signal from an upstream broadcast network.

For instance, the GPS coarse-acquisition ( C / A ) code broadcast in the L1 signal changes phase at, but the L1 carrier itself is 1575. 42 MHz, over a thousand times as fast.

The avionics system included a 133 MHz Pentium flight computer running Linux, using 802. 11 telemetry broadcast via custom-made cylindrical patch antennas, a GPS module, IMU module, temperature sensor, altimeter, and recovery node.

Technical accessories include cyclocomputers for measuring speed, distance, heart rate, GPS data etc.

Raymond is currently the admin of the project page for gpsd, a daemon that makes GPS data from a receiver available in JSON format.

The Performance Improvement Program variant, K55A1, is a complete domestic overhaul of the K55 which is further augmented by Samsung Thales with modern digital ballistic computers, multifunctional data display and controllers, GPS navigation and target acquisition system, wireless datalink equipment, and upgraded fire control storage battery and power supply unit, to closely match the US military's modernization of the Paladin into next-generation standard.

On most modern ships the GPS or other navigational aids feed data to the gyrocompass allowing a small computer to apply a correction.

Example of modern equipment for surveying ( Field-Map technology ): GPS, laser rangefinder and field computer allows surveying as well as cartography ( creation of map in real-time ) and field data collection.

* TrailGuru-Community project designed to build a digital database of trails using GPS data

* Precise Point Positioning, a GPS data processing technique

Note that the contour line data or any other sampled elevation datasets ( by GPS or ground survey ) are not DEMs, but may be considered digital terrain models.

Augmented reality ( AR ) is a live, direct or indirect, view of a physical, real-world environment whose elements are augmented by computer-generated sensory input such as sound, video, graphics or GPS data.

Many of these cameras however, are owned by private companies and transmit data to drivers ' GPS systems.

An increasing number of vehicles are equipped with in-vehicle GPS ( satellite navigation ) systems that have two-way communication with a traffic data provider.

This enhanced data allowed for considerably enhanced system accuracy ( not unlike Selective Availability < SA > under GPS ).

Mobile GIS conflates GIS, GPS, location-based services, handheld computing, and the growing availability of geographic data.

To obtain wind data, they can be tracked by radar, radio direction finding, or navigation systems ( such as the satellite-based Global Positioning System, GPS ).

Global Positioning System ( GPS ) navigation satellites transmit electronic ephemeris data consisting of health and exact location data that GPS receivers then use ( together with the signal's elapsed travel time to the receiver ) to calculate their own location on Earth using trilateration.

Additional unused capacity is used by some broadcasters to transmit utility functions such as background music for public areas, GPS auxiliary signals, or financial market data.

NMEA 0183 is a combined electrical and data specification for communication between marine electronic devices such as echo sounder, sonars, anemometer, gyrocompass, autopilot, GPS receivers and many other types of instruments.

* GPS navigation device is sometimes added to the handlebars and is used to display and monitor progress on trails downloaded from the internet or pre-made mapping systems, record trails on the fly, and keep track of trip times and other data.