Global Positioning System (GlobalPositioningSystem). Simply put, this is a satellite system consists of 24 satellites covering the globe composition. This system ensures that at any time, at any point on Earth can be observed simultaneously to four satellites, the satellite can be collected to ensure that the latitude and longitude and the height of the observation point, in order to achieve the functions of the navigation, positioning, timing and the like. This technology can be used to guide aircraft, ships, vehicles and personal, safe and accurate along the selected route, arrive on time.
1, related presentations
GPS navigation system
GPS navigation system is based on global positioning satellites 24 based on the global around the three-dimensional position information, such as three-dimensional velocity around the clock in a radio navigation system. It consists of three parts, one ground control section, by the master station, terrestrial antenna, communication stations and auxiliary systems. Second, part of the space, consists of 24 satellites, distributed in six orbital planes. Third, the user device section, a GPS receiver and a satellite antenna. Civilian positioning accuracy within 10 meters up to now.
GPS navigation system, built-in GPS antenna receives the data transmitted in the at least three 24 GPS satellites from around the Earth, combined with the electronic map stored in a car navigation system, by GPS satellite signals to determine the location coordinates of this match were to determine the exact position of the vehicle in the electronic map, which is usually referred to positioning.
on the basis of positioning, the monitor can be multifunctional, providing the optimum route, the road ahead and the nearest gas station, restaurants, hotels and other information. Unfortunately, if the GPS signal is interrupted, and therefore you lost, do not worry, GPS has recorded your route, you can backtrack. Of course, these functions are inseparable from the region has been pre-programmed using mapping software.
Car GPS feature is also a great anti-theft, anti-theft divided into static and dynamic track two. The former refers to the ownerLeave the car parked vehicles suffered theft, destruction, move the vehicle to alert the GPS monitoring center through its own monitoring system, and automatically contact the owners of cell phones, telephone alarm. The latter can be placed on the exercise of the stolen vehicle location tracking, condition monitoring, car track record, and even control the vehicle off, broken oil. Function
2, GPS navigation system
The main purpose of global positioning system: (1) terrestrial applications, including vehicle navigation, emergency response, atmospheric physical observations, geophysical exploration, engineering surveying, deformation monitoring, crustal movement monitoring, municipal planning and control; (2) marine applications, including the best ocean-going voyage route determination, real-time scheduling and ship navigation, marine rescue, marine treasure hunters, hydrogeological measuring and positioning of offshore platforms, sea-level monitoring; (3) aerospace applications including aircraft navigation, aerial remote sensing attitude control, LEO satellite orbit, missile guidance, air rescue and manned spacecraft protection detection.
3. The composition of
the GPS global satellite positioning system consists of three parts:
space portion mdash; mdash; mdash; GPS constellation; the GPS of a space portion is composed of 24 satellites (21 operational satellites; 3 spare satellites), which is located above the surface over 20200km evenly distributed in the, orbital inclination six orbital planes (four per orbital plane) is 55deg; . Such that the distribution of satellite anywhere in the world, can be observed at any time more than four satellites, and can be stored in the satellite navigation message, GPS satellites because of problems such as atmospheric friction; Over time, the accuracy of navigation will gradually decrease . .
2 ground control system
ground control segment mdash; mdash; mdash; ground monitoring system; monitoring station by a ground control system (MonitorStation), master control station (MasterMonitorStation), ground antenna (GroundAntenna) composed of the main control station located in Colorado Springfield (ColoradoSpring). By the satellite ground control station is responsible for collecting the pass messages back and calculate the satellite ephemeris, the relative distance, atmospheric correction data.
user segment mdash; mdash; mdash; GPS signal receiver. That part of the user equipment GPS signal receiver. Its main function is to capture certain satellite can be cut-off angle to be measured to the selected satellite, and keeps track of these satellites. When the receiver to capture the satellite signal tracking, can measure the rate of change of the receiving antenna to the satellite pseudo distance and distance, demodulated satellite orbit parameters and other data. Based on these data, the micro-computer processing in the receiver can be positioned by the solution method for positioning calculation, the calculated latitude and longitude, altitude, speed, time and other information of the user’s physical location. Receiver hardware and software post-processing package and the GPS data of a complete GPS user equipment. A GPS receiver is divided into two parts of the antenna unit and the receiving unit. Receivers typically within and outside the aircraft using the two kinds of DC power supply. Purpose machine that is provided within the power supply without interrupting the continuous observation replacing external power. Automatically charging the battery in the external power supply with the machine timing. Machine shutdown battery powered RAM memory, to prevent data loss. Various types of machine currently receiving volume smaller, more light weight, easy to use field observation. Secondly, compared with the user receivers, two kinds of conventional single-frequency and dual-band, but due to the price factor, the general user purchases multiple single frequency receivers
4 the basic principle, the principle
GPS navigation system is a satellite position measurement of a known distance between the user receiver and the integrated data of a plurality of satellites the receiver can know the specific position. To achieve this purpose the position of the satellite in the satellite ephemeris may be isolated according to the time recorded by onboard clock. And to the satellite from the user record of the satellite signal is propagated throughTo time experienced by the user, and then multiplied by the speed of light to get (due to the interference of the atmosphere ionosphere, this distance real distance between the user and the satellite is not, but pseudorange (PR): When the GPS satellite is working properly There are two pseudo-code, will continue to emit a pseudo-random code binary 0 and 1 symbols composition (referred to as pseudo-code) .GPS system uses the navigation data, namely civilian C / a code and military P (Y ) code .C / a code frequency of 1.023 MHz, repetition period of one millisecond, microsecond symbol spacing, corresponding to 300m; P code frequency 10.23 MHz, repetition period of 266.4 days, 0.1 microsecond symbol spacing, and Y codes corresponding to 30m. is formed on the basis of the P code, better security performance. navigation data including satellite ephemeris, work status, clock corrections, ionospheric delay correction, atmospheric refraction correction and other information which is demodulated from the satellite signals, at 50b / s modulation in each of the main frame includes carrier frequency transmitted navigation message frame length for each of five subframes each of three frames 10 6s word; after repeated every thirty seconds, updated hourly… two were 15000b. content main navigation message away Test code, code conversion, data blocks 1, 2, was the most important ephemeris data. When the user receives the navigation data, and satellite time is extracted with its own clock that can do comparison from the satellite to the user, and then using the satellite ephemeris data estimated navigation message when the location of the satellite transmit message, the user position information in speed WGS-84 geodetic coordinate system can be learned.
[123 ] Function GPS navigation system satellites visible portion is continuously transmitted navigation data. However, since the user accepts clock and satellite on a carrier machine clock can not always synchronized, so in addition to the user three-dimensional coordinates x, y, z, but also to introduce a Delta; t, i.e. the time between the satellite and the receiver as the difference between the unknown solution and then out of these four unknowns with four equations so if the receiver wants to know the position of which, at least four satellites can be received. signal
GPS receiver may receive time information can be used to accurately timing when nanosecond;. ephemeris prediction for the next few months in which the approximate location of the satellite; means for calculating Satellite broadcast ephemeris desired coordinate position, the accuracy of several meters to tens of meters (different from each satellite, at any time change); and GPS system information, such as satelliteStatus.
GPS receiver to measure the code can be obtained from the satellite to the receiver, since the receiver containing the satellite clock errors and atmospheric propagation errors, it is called pseudorange. 0A of the measured pseudorange code called UA code pseudorange, about about 20 meter accuracy, to the P code pseudorange measured referred to as P code pseudo range, accuracy of about 2 meters.
GPS receiver receives satellite signals, decoding, or other techniques employed, after the information modulated on a carrier is removed, it can be recovered carrier. Strictly speaking, the phase of the carrier shall be referred to as carrier beat phase, which is the difference received by the Doppler shift of the satellite signal carrier phase influence the receiver local oscillation signal phase of. Typically measured at the receiver clock to determine the time epoch, keeping track of the satellite signal, the phase change values can be recorded, but the initial value of the satellite receiver and the oscillator phase at the beginning of the observation is not known, from beginning phase integer epoch is not known, i.e., integer ambiguity, only as parameters in a data processing solver. High precision phase observations to millimeter, but only solved ambiguity, only the relative positioning and to use the phase observations when there is a continuous observations, and to achieve better positioning accuracy of meter-only phase observations can be employed.
by positioning mode, GPS positioning into a single point and relative positioning (DGPS). Single point positioning receiver position is determined according to the observational data of a receiver mode, it can only use pseudorange measurements, can be used for travel and other navigation and positioning of the schematic. Relative positioning (DGPS) is a method to determine the relative position between the observation point according to the observations of two or more receivers, both can be measured pseudorange phase observables may also be employed, or engineering geodetic measurements are made using phase observations relative positioning.
GPS observables are included in the receiver and the satellite clock error, atmospheric propagation delay, multipath error, etc., but also by the satellite broadcast ephemeris error in the position calculation is performed relative positioning when most of the common errors are canceled or weakened, thus greatly improving the positioning accuracy, dual-frequency receiver offset may be measured in the atmosphere of a main portion according ionospheric error View two frequencies in high precision, between distant receiver when (atmospheric significantly different), should be used in dual-frequency receiver.
5, function and use of
The main purpose of a global positioning system: (1) terrestrial applications, including vehicle navigation, emergency response, physical observations of atmospheric, geophysical exploration, measurement engineering, deformation monitoring, crustal movement monitoring, municipal planning and control; (2) marine applications, including the best ocean-going voyage route determination, real-time scheduling and ship navigation, marine rescue, marine treasure hunters, hydrogeological measurements and positioning of offshore platforms, sea level lift monitoring; (3) aerospace applications including aircraft navigation, aerial remote sensing attitude control, LEO satellite orbit, missile guidance, air rescue and manned spacecraft protection detection.
mainly for positioning navigation of ships, automobiles, aircraft and other moving objects.
Construction Machinery (RTG, bulldozers, etc.) control applications.
road works is also applied.
6, type
Many types of the GPS satellite receiver, according to the model is divided into geodesic type total station, timing pattern, handheld, integrated; The use is divided into vehicle-mounted, ship type, airborne-style, on-board type, spring-loading.
Use according to the classification of the receiver
1. The navigation receivers
This type of navigation receiver motion vectors are mainly used, which can give the real-time position of the carrier and speed. Such receivers typically employ C / A code pseudorange measurement, a single point of real-time positioning accuracy is low, typically plusmn; 10m, when impact is plusmn SA; 100m. Such receivers are cheap, widely used. Depending on the application, and such receivers can be further divided into:
type vehicle mdash; mdash; for a vehicle navigation and positioning;
type navigation mdash; mdash; for ship navigation Location;
aviation type mdash; mdash; for aircraft navigation and positioning. Due to the fast speed aircraft, therefore, on the aviation requirements for the receiver can adapt to high-speed movement.
onboard type mdash; mdash; for satellite navigation and positioning. Since the speed of the satellite up 7km / s or more, more demanding receiver.
2. Geodetic receivers
geodetic receivers mainly used for precision engineering and precision geodetic measurements. Such instruments mainly carrier-phase observations relative positioning, high positioning accuracy. Instrument structure is complex, expensive.
3. Timing receivers
The main use of such a receiver provided with high precision time standard GPS satellite time service, Observatory commonly used in radio communications and time synchronization.
4.2.2 Classification by the carrier frequency of the receiver
single-frequency receiver
Single-frequency receiver can receive the L1 carrier signal, measuring the carrier phase observations positioning . Since not effectively eliminate the influence ionospheric delay, applies only to single-frequency receivers short baseline (lt; 15km) precise positioning.
dual receiver
The receiver may receive a dual simultaneously L1, L2 carrier signal. Not the same as using the dual delay of the ionosphere, may be eliminated ionospheric delay of the electromagnetic wave signal, so the receiver can be used for dual precise positioning thousands of kilometers.
4.2.3 Classification by the number of receiver channels
GPS receiver can receive signals of multiple GPS satellites simultaneously, different satellites in order to separate the received signals to enable tracking of the satellite signal processing and measurement, the device has a function referred to as antenna signal path. The receiver has a channel type can be divided into:
Multi-channel receiver
Sequential channel receiver
Multi-channel multi-channel receiver
[123 ] 4.2.4 classification works by the receiver
codes associated receivers
code-dependent code related art receiver using pseudorange observations obtained.
receivers square
FlatSquare square art receiver using the modulated signal to remove the carrier signal, the carrier signal to recover the full measured phase difference between the carrier signal generated within the receiver with the received signal carrier phase, pseudorange measurement observations.
Mixed receiver
This instrument is an integrated advantages of the two receivers, can be obtained either pseudorange code phase can be obtained carrier phase measurement.
Interference type receiver
Such a receiver is a GPS satellite as a radio source, interferometric measurement method, measuring the distance between two stations.
After 20 years proved, GPS system is a high-precision, multi-system radio weather and global navigation, positioning and timing. GPS technology has developed into a multi-field, multi-mode, multi-purpose, multi-model international high-tech industries.
GPS timing signals provide a corrected global positioning system GPS satellites provide latitude, longitude and altitude information, accurate distance measurements requires an accurate clock. Therefore, we must use precise GPS receivers relativistic effect. Accuracy within 30 meters of the GPS receiver means that it has used the relativistic effects. Physicists at the University of Washington CliffordM.Will explained in detail: ldquo; if you do not consider relativistic effects, satellite clock on the Earth and on the clocks are not synchronized. rdquo; relativistic that fast moving objects over time slower than static. Will calculated for each GPS satellite across about 1.4 million kilometers per hour away, which means it’s onboard atomic clock 7 microseconds slower than clocks on Earth every day. The gravitational force exerted on time more relativistic effects. About 2 million meters of altitude, by the gravitational pull of GPS satellites by about a quarter on the ground. The result is fast onboard clock 45 microseconds per day, GPS should be included deviation of 38 microseconds. Ashby explained: ldquo; if no satellite frequency compensation, the error will increase 11 km per day. rdquo; (in fact this effect is more complicated, because the satellite along an eccentric orbit, and sometimes close from the earth, sometimes further away.)
7, the associated entries
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