Navigation with GPS
Navigation with GPS
The use of satellites for navigation or positioning purposes is as old as the history of artificial satellites. This satellite principle is based on the Doppler shift of the frequency of the signal coming from the object. That is, a signal is sent to an object via satellite to determine the position of an object on Earth, and it is possible to know the position of an object on Earth with the help of the frequency of the received signal after that signal is bound to the object. The United States launched the first navigation satellite into space in 1986, known as the "Transit System." Initially this system was usually used for defense purposes. But since 196 it has been used for all normal purposes.
In the last decade, a new type of satellite based navigation system has been invented which is known as Global Positioning System or GPS. This system allows you to accurately represent the current position of an object. GPS is a radio-based navigation system that can provide detailed information about the three-dimensional position of the earth in all types of weather, even 24 hours a day. With the help of a commercial GPS locator, a user can find out his location on the earth.GPS usually has three main parts, namely the space segment, the control segment and the user segment.
The space segment is a collection of 24 Navstar satellites orbiting the Earth in six orbits at a distance of 11,000 nautical miles from the Earth's surface. The planes of these orbits have an angle of 60 degrees with each other and at an angle of 55 degrees with the equator.Of the 26 Navstar satellites in the space segment, 21 are functional satellites and the remaining three are standby satellites. The U.S. Department of Defense controls these Navstar satellites and this system is an established and widely used system for all GPS users around the world.The control segment consists of five monitoring stations that help transmit satellite data. This sent or transmitted data includes the location of the satellite as time function, time accuracy and other broadcast message data. The monitoring station secretly monitors the activity of all GPS signals to determine satellite control and orbit.
The user segment includes receivers that are usually controlled or deployed in aircraft, ships, tanks, submarines, etc. Receivers are used to detect, de-encode and process GPS satellites and to express satellite signals in the form of position, velocity and time functions. The position of the object held by the receiver consists of the angular distance and longitude from the equator which is then changed to various data and coordinate systems to determine the position of the object.GPS creates a lot of excitement in the use of satellites and is able to bring about a revolutionary change. The idea of using satellites for navigation dates back to the launch of the first satellite, Sputnik-1, in 1985.
The GPS system works based on the measurement of the distance between the receiver and the satellite. A satellite emits a signal with the position and time of an object every 3 nanoseconds with the help of four perfect own clocks. The receiver can retrieve information about the location of the object sent by the transmitting satellite.
If the distance of an object from a satellite is known, then the position of the object on the surface of the imaginary sphere centered on the satellite and the radius of that imaginary sphere is equal to the distance of the satellite from the receiver. If the position of the object is known from two satellites, then the position of the object will be on the intersected line of the imaginary sphere and if any other third measurement method is readily available, it can be seen that the object can be in only two positions. Any one of these locations is virtually impossible and GPS method has been able to overcome this impossible location.
There are usually two types of GPS systems. The first is called the standard positioning system and the second is called the precise positioning system. Authorized users, such as members of the military who have high quality receivers, access this precision positioning system, where the accuracy is close to 1mm. Ordinary users, on the other hand, use a standard positioning system where the accuracy is close to 100mm.
There is also a differential GPS system that uses a permanent reference station to reduce the position error and help to keep the accuracy or error amount close to 10m.
The Kinematic GPS system is one of the most sophisticated GPS systems in use today. It usually uses carrier phase observation and reduces the amount of error to bring it closer to the centimeter level.
Russia has its own navigation system known as the Global Navigation Satellite System. The system has about 24 satellites orbiting in three orbits.
The invaluable contribution of GPS systems has been proven in the US military service. Troops or tank and aircraft users usually use GPS receivers to learn about enemy or allied locations. For example, F-16 fighters, kc-135 aerial riflers and B-2 bombers, where GPS receivers are used. All of these systems were used extensively by American troops during the Gulf War. As a result, it enables troops to successfully carry out combat tactics in the desert.
With the advent of ever-new technology and the amount of positioning error coming down to around 1cm, the horizon / range of GPS systems is constantly increasing.
