GPS and relativity relationship
We should thank Einstein, his theory makes the astonishing new device to become a reality! Design GPS satellite scientists must consider relativity brings time dilation effect and relativity the passage of time rate and the relationship between dimensions.
GPS constitute
Space part 1.
GPS space part is composed by 21 star, it is located at work from satellite ground 20200km above, evenly distributed in 6 rail surface (each track surface 4 star), orbit for 55 ° Angle. In addition, there are also three star active spare satellite orbit. The distribution of the global satellite makes anywhere at any time can be observed 4 star above the satellite, and able to be in in the satellite navigation of stored information. GPS satellite for atmospheric friction problem, with the passage of time, the attitude accuracy will gradually reduced.
2. Ground control system
Ground control system by hand Statio), Master hand now, Ground of Antenna, the main control Station, colo springfield, (Colorado are). Responsible for collecting ground control station by satellite information is calculated, and satellite star calendar, relative distance, atmospheric correction of the data.
3. User equipment parts
User equipment parts namely GPS signal receiver. Its main function is able to capture by certain satellite cut-off Angle to choose to be measured satellite, and tracking these satellites running. When the receiver captures tracking satellite signal after, can measure the receiving antenna to satellite pseudo distance and distance rate, satellite orbits parameters, such as the demodulation data. According to the data, the micro computer receiver can press positioning the method for calculation, locate in the user's geographical longitude and latitude and altitude, speed, time and other information. Receiver hardware and software inside machine and GPS data post-processing software packages to form a complete GPS user equipment. GPS receiver unit and receiving antenna structure is divided into two parts unit. Receiver generally adopted inside machine and turned two dc power. Set inside machine power aims to replace the power supply without interrupting continuous observation. In use within the battery power time turned automatically charges. Shutdown, inside machine battery for RAM memory power supply, in order to prevent the loss of data. At present various types of accept machine volume smaller and smaller, more and more light weight, easy to use the field observation. Second, for the user receiver, the existing single-rate with dual-frequency two, but due to the price factor, general user buys more for single-rate receiver.
GPS term
1.GPS Generalized Processor Sharing
2.GPS Global Positioning System
3.[GPSS]General Purpose Systems Simulator
4.[DGPS]Differential
5.GPS General Phonetic Symbols
GPS principle
GPS navigation system of basic principle is measured known position of satellite to the distance between the user receiver, and then integrated many satellite data so that you may know the location of the receiver. To achieve this objective, satellite positions may, according to the records of space-borne clock time in satellite star calendar found.
Visible GPS navigation system satellite partial role is to continually launch navigation message. However, due to the user acceptance machine use clock and satellite space-borne clock may not always synchronization, so in addition to user 3d coordinate x, y, z) outside, will also introduce a Δ t namely and satellite receiver between the Windows as unknown, then use four equations will these four unknown solve it. So if you want to know receiver's place, at least receives four satellite signal.
GPS receiver can receive the accurate and can be used in shoushi nano seconds time information; level Used to forecast the next few months in compendium of satellite location prediction star calendar, Used to calculate when positioning satellite radio star of coordinates required for a few meters calendar, precision to tens metres (each satellite is different, change); And GPS system information, such as satellite condition and so on.
GPS receiver to yards of measurement can get satellite receiver distance, due to contain clock error and satellite receiver atmospheric transmission error so called the pseudorange. To 0A yards of measured pseudorange called UA yards pseudorange, precision is about 20 meters of P yards of measured pseudorange called P yards pseudorange, precision is about 2 meters.
GPS receiver of received signal of satellites, decoding or adopt other technology, will modulation in carrier of information on the removed, can return to carrier. Strictly speaking, the carrier phase should be called carrier clap frequency phase, it is received by the doppler frequency influence of satellite signal carrier phase and receiver this machine oscillations produce signals phase difference. General in the receiver clock determine precessed moment measure, to maintain a satellite signal tracking, can record the phase change value, but when begin to observe the receiver and satellite oscillator initial phase is did not know, starting precessed phase integer is also don't know, namely the whole week fuzzy degrees, only in data processing as parameters for calculating. Phase observation data of high precision to mm, but the premise is to work out a full week fuzzy degrees, so only in relative positioning, and have a period of continuous observation value can use the phase observation data, and to achieve superior meter scale positioning accuracy of also can adopt phase observations.
According to the localization way, GPS positioning divided into the single point positioning and relative location (differential positioning). According to a single point positioning receiver is the observation data to determine the receiver position way, it can only using pseudorange observed quantity, can be used to transport a compendium of navigation and positioning, etc. Relative positioning (differential positioning) is based on two VCRS receiver of observation data to determine the relative position between the observation methods, it can be adopted pseudorange observed quantity also can use phase observation quantity, geodesy or engineering measurement shall be made phase observation value is relative positioning.
In GPS observation amount contains the satellite and the receiver's clock is poor, atmospheric propagation delay, multipath effect etc, in positioning error computation but also by satellite radio star calendar error, the influence of the relative positioning, most public error was offset or weakened, therefore positioning accuracy will rise greatly, double-frequency receiver can according to two frequency offset the observed quantity atmosphere ionosphere error of the main parts in the precision requirement, high, receiver distance between (atmospheric significant difference), should choose double-frequency receiver.
GPS prospects
Because of GPS technology have all-weather, high precision and automatic measurement features, as advanced measuring method and new productive forces, have been integrated into the national economic construction, national defense construction and social development in various applications.
With the end of the cold war and global economic boom, the us government announced the 2000 and 2006 period, in that the us national security not threatened premise, cancel SA policy, GPS civil signal precision in the global scope improved, using C/A code of A single point positioning accuracy by 100 meters improve to 10 metres, which will further promote GPS technology applications, improve productivity, working efficiency, scientific level as well as the people's quality of life, stimulate GPS market growth. Experts predict, in America, only the GPS navigation system, after 2000 market will reach $30.
GPS characteristics
The global positioning system key features:
(1) the world, all-weather work.
(1) the higher precision. Single positioning accuracy than 10m, the differential positioning, precision can reach the cm-level and mm level.
2 the function is much, wide application.
GPS system features: high precision, all-weather, high efficiency, multi-function, simple operation, wide application, etc.
1, higher precision
Application has proved that GPS positioning accuracy in relative 50KM within could reach 10-6,100 day - 500KM could reach 10-7,1000 KM can reach up to 10-9. At 300-1500M engineering precision positioning, 1 hour above observation solution its plane its plane position error is less than 1mm and ME - 5000 electromagnetic rangefinder determination to compare, its length of side poorer maximum 0.5 mm, school sent the error in of 0.3 mm.
2, the observation time is short
With the continuous improvement of the GPS system, software update ceaselessly, at present, within 20KM relatively static positioning, only 15-20 minutes; Rapid static relative location measurement, when standing apart with each starting in within 15KM benchmark, starting observation time only 1-2 minutes and then may at any time positioning, each station observation that it only takes a few seconds.
GPS function
The global positioning system of main use: (1) land application, mainly including vehicle navigation, emergency response, atmospheric physics observation, geophysical resource exploration, project survey, deformation monitoring, crustal movement monitoring, municipal planning control, etc.; (2) Marine applications, including features not best voyage routes determination, real-time scheduling and navigation ships, Marine rescue, Marine exploration treasure, hydrology geology measurements and offshore orientation, sea-level fluctuation monitoring etc., (3) aerospace applications, including airplane navigation, aviation remote sense attitude control, Leo satellite orbit determination, the missile guidance, aviation rescue and manned spacecraft protective detection, etc.
GPS application
Primarily for ship, automobile, airplane movement on objects orientation navigation. For example:
1. The ocean ship navigation and enter the port water diversion
2. Aircraft route guidance and approach the landing
3. Auto autonomous navigation
4. Ground vehicles tracking and urban intelligent transportation management
Emergency rescue 5.
6. Personal travel and outdoor adventure
7. Personal communications terminal (with mobile phones, PDA, electronic map integrated integration)
1. Electric power, telecommunications, communications and other network time synchronization
2. The exact time of the award
1. Various grades of geodesy, control measures
2. Roads and various line lofting
3. Accurate frequency granted access
3. Underwater topography measurement
4 the crustal deformation measurement, DAMS and large building deformation monitoring
5. GIS application
6. Engineering machinery (tyre crane, bulldozer, etc) control
Precision agriculture 7.
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