Basics of the GPS navigation system.
Basics of the GPS navigation system.
The abbreviation GPS stands for Global Positioning System. GPS navigation systemsare based on the technology of receiving signals from satellites. In this case, the distance between the satellite at the time of emission and the object receiving the signal is calculated. Registration of the time of passage of the radio signal and information about the speed of its propagation allows us to determine the distance to the radiation source. For the operation of the GPS navigation system, the position of the satellites in orbit must be known at any given time. For the correct calculation of coordinates, precise time reference and synchronization of clocks on satellites and in navigation receivers are necessary. For this, on the satellites of the GPS GSM systemAtomic clocks are set with an accuracy of one nanosecond. To set the clock to run more correctly, navigation receivers use special algorithms for processing signals received simultaneously from four satellites. This is how the location of an object is determined, i.e. its latitude, longitude and altitude above sea level are determined, as well as the direction and speed of its movement. Gps gsm systemsconsist of a complex of artificial Earth satellites and ground tracking stations, grouped according to a common principle. The satellite system is called NAVSTAR. The subscriber equipment of the gps gsm system consists of individual GPS receivers capable of receiving signals from satellites and, according to the information received, calculating their location. The Russian analogue of the system that performs such functions is called GLONASS.
GPS monitoring system
The NAVSTAR satellite system includes 24 artificial Earth satellites located in 6 different circular orbits. These orbits are located at an angle of 60 degrees to each other. The orbital period of one satellite is 12 hours. The weight of each satellite is about 787 kg, the size is more than 5 m, including solar batteries. Each satellite has an atomic clock, a computing encoding device and a 50 W transmitter emitting at a frequency of 1575.42 MHz. GPS monitoring systemNAVSTAR appeared in February 1978, when the first satellite of the system was launched into orbit. The average service life of one satellite is approximately 10 years, so the program includes the constant production and launching of new satellites into orbit to replace those that have failed and exhausted their operating limit. GPS monitoring system, based on the operation of these satellites, receives signals every second that report information about the status (i.e. condition) of the satellites, the current date, time, almanac data, and the exact time of sending all messages. GPS monitoring systemimplies the presence of a special almanac, which contains information about where in the celestial sphere each satellite should be at any given time during the day, i.e. orbital data of all satellites.
GPS monitoring systemcan operate on the basis of a mechanism for constant data correction, since the speed of propagation of radio signals is constant and equal to the speed of light, the distance to the satellites is determined by the delay in the time of reception of the message by the GPS receiver relative to the time of sending the message from the satellite. To accurately determine this delay, the clocks on the satellites and the clock in the GPS receiver must be synchronous, which is ensured by synchronizing the receiver clock using information contained, as indicated above, in the satellite signals. GPS monitoring systemis characterized by a minimal possibility of error. An error was introduced a priori into the satellite signals, allowing the location to be determined with an accuracy of 30 — 100 m, although in principle the accuracy of the GPS system can reach several centimeters. Since May 2000, this mode has been disabled. Other sources of error are unsuccessful geometry of the mutual arrangement of satellites, multipath propagation of radio signals, ionospheric and atmospheric delays of signals, etc.
GPS control system
GPS control systemallows you to determine the location at any point on land, at sea and in near-Earth space. In general, the entire range of GPS receiver models can be divided into four large groups: personal GPS receivers for individual use — they are characterized by small dimensions and a wide range of service functions. For example, they are equipped with the ability to form and calculate routes and functions for receiving and sending e-mail. Gps control systeminstalled on the car: car GPS receivers, which are designed for installation in any land vehicle and have the ability to connect external receiving and transmitting equipment for automatic transmission of traffic parameters to control centers. This is the basis for satellite monitoring of transport. Marine GPS receivers equipped with an ultrasonic echo sounder, as well as additional replaceable cartridges with cartographic and hydrographic information for specific coastal areas. Aviation GPS receivers used for piloting aircraft, including commercial aviation. GPS control system has a large number of auxiliary services and systems with a high level of positioning accuracy. These primarily include wide-area and regional differential subsystems. The former include WAAS (Wide Area Augmentation System) on the American continent, European EGNOS and Japanese MSAS, which transmit correction information to user receivers via geostationary satellites.