source:truck tracking webfleet solutions release time:2022-11-26 Hits: Popular:realtime gps tracker online
At the end of the 1950s, the former Soviet Union launched the first man-made earth satellite of mankind. American scientists discovered the phenomenon of Doppler frequency shift in their tracking and research, and used this principle to facilitate the establishment of the Doppler satellite navigation and positioning system TRANsIT, which has achieved great success in military and civil aspects. It is a leap in the history of navigation and positioning. China has also introduced several Doppler receivers, which are used in island joint survey Earth exploration and other fields. However, due to the low orbit height and signal carrier frequency of the Doppler satellite, it is difficult to improve the orbit accuracy, which makes the positioning accuracy low to meet the requirements of geodesy or engineering survey, and it is impossible to apply it to the research of astrogeodynamics. In order to improve the accuracy of satellite positioning, the United States began to build the Global Positioning System (GPS) in 1973. After entering the phase of scheme demonstration and system test, the official working satellite was launched in 1989, and was completed and put into use in 1994. The space part of the GPS system is composed of 21 satellites, which are evenly distributed on 6 orbital planes. The ground height is more than 20000 km, the orbital inclination is 55 degrees, the flat heart rate is about 0, and the period is about 12 hours. The satellite transmits carrier signals of two bands to the ground. The carrier signal frequencies are 1575.442 MHz (L1 band) and 1227.6 MHz (L2 band) respectively. The satellite is equipped with atomic clocks with high accuracy to ensure the stability of the frequency, The broadcast ephemeris representing satellite position, C/A code and P code used for ranging, and other system information are modulated on the carrier wave, which can provide high-precision, all-weather, continuous, real-time three-dimensional velocity measurement, three-dimensional positioning, and time service to any number of users worldwide.
The control part of the GPS system consists of five monitoring stations located in the United States. These stations continuously observe the GPS satellites and update the calculated and predicted information from the injection station to the satellite information.
The users of the GPS system are very invisible. It is a one-way system, and users only receive signals without transmitting them. Therefore, the number of users is unlimited. Although the GPS system was built for military purposes at the beginning, it has been rapidly developed in civilian areas, and various GPS receivers and processing software have emerged. At present, the receivers in the Chinese market mainly include NovAtel, ASHTECH, TRIMBLE, CMC, etc. The receiver that can observe two frequencies is called dual frequency receiver. The receiver that can only observe one frequency becomes single frequency receiver. They are quite different in accuracy and price.
For users in the surveying and mapping field, GPS has caused revolutionary changes in the field of surveying and mapping. At present, the control network or deformation monitoring network covering several kilometers to thousands of kilometers, with positioning accuracy ranging from hundreds of meters to millimeters, generally use GPS as the preferred means. With the maturity of RTK technology, GPS has begun to penetrate into decimeter and even centimeter level lofting, high-precision dynamic positioning and other fields.
Since 1992, IGS, an international GPS geodetic and geodynamic service, has established multiple data storage and processing centers and more than 100 perennial observation stations around the world. China has also set up a number of perennial observation stations in Shanghai Yushan, Wuhan, Xi'an, Lhasa, Taiwan, etc. The observation data of these stations are transmitted to the data storage center in the United States every day through the Internet. IGS also integrates the results of each data processing center almost in real time, And participate in the global coordinate reference system maintenance of the international earth rotation service IERS and the release of the earth rotation parameters. Users can also obtain observation data, precise ephemeris and other products from INTERNET for free.
The real-time navigation and positioning accuracy of the GPS system is very high. The United States has implemented the so-called SA policy since 1992, that is, to reduce the accuracy of satellite positions in broadcast ephemeris, to reduce the accuracy of clock correction numbers, to add high-frequency jitter to the satellite reference frequency (reducing the measurement accuracy of pseudo range and phase), and then to implement the A-S policy, that is, to change the P code to Y code, which further restricts the precision pseudo range measurement, The US military and licensed users are not affected by these policies, but in order to obtain greater commercial benefits, these policies will eventually be cancelled.
Read recommendations:
mini gps tracker Manufacturing
gps vehicle tracker wholesaler
Why do cars load a car GPS positioner.rastreador de GPS wholesale
Last article:GPS positioning principle
Next article:The strategic role of satellite positioning system and commercial interests
Related Information
mileage tracking webfleet solutions
2023-03-164G obd gps trackewr
2023-03-16Dog gps tracker supplier
2023-04-23fleet gps trackers maker
2023-04-23fleet gps trackers price
2023-04-23GPS Tracker wholesaler
2023-03-16fleet tracking mobile app
2023-03-16fleet gps trackers Solution
2023-04-23gps tracker for kids supplier
2023-04-23Best hidden gps trackers
2023-04-11NB20 -4G Bluetooth Smart Pet Tracker
2022-06-21Mini Sized GPS Tracker PCBA
2022-06-17G500L -4G OBD GPS Tracker
2022-09-06GF20-Mini Magnet GPS Tracker
2022-06-21G200NY -Cow/Camel GPS Tracker
2022-06-21How to prevent the disassembly of the car GPS locator?personal gps tracker manufacturer
2023-03-15Composition and characteristics of GPS system
2022-11-07Overview of the car navigation system.Magnetic gps tracker Manufacturing
2023-05-18Advantages of traditional GPS and new technology GPS solutions
2022-10-15What is the difference between vehicle-mounted GPS locator and vehicle-mounted GPS?Fleet management
2023-03-23What are the precautions for installing the car GPS positioner
2023-02-25GPS positioning function
2022-12-10GPS position difference principle
2022-10-11The suction cup of GPS bracket is easy to loosen the problem.realtime gps tracker online Manufacturi
2023-04-12GPS vehicle tracking and dispatching function
2022-12-01Introduction and Comparison of GPS PPS Technology and Other Clock Synchronization Technologies
2022-11-11What is the function of gps tracker.mileage tracking webfleet solutions
2023-03-13GPS map upgrade
2022-09-26Why does China Beidou dare to compete with the first tier GPS team?
2022-11-17GPS system composition
2022-12-05