Technology and application of gps satellite navigation system. Satellite navigation systems

creations satellite navigation was born in the 50s. At the moment when the USSR launched the first artificial Earth satellite, American scientists led by Richard Kershner observed the signal coming from the Soviet satellite and found that due to the Doppler effect, the frequency of the received signal increases as the satellite approaches and decreases as it moves away. The essence of the discovery was that if you know exactly your coordinates on Earth, then it becomes possible to measure the position of the satellite, and vice versa, knowing the exact position of the satellite, you can determine your own coordinates.

This idea was realized after 20 years. The first test satellite was launched into orbit on July 14, 1974 by the United States, and the last of all 24 satellites needed to completely cover the earth's surface was launched into orbit in 1993, thus the Global Positioning System or GPS for short came into service. It became possible to use GPS to accurately target missiles to stationary, and then to moving objects in the air and on the ground. Also, with the help of a system built into satellites, it became realistic to determine powerful nuclear charges located on the surface of the planet.

Initially, GPS - global positioning system, was developed as a purely military project. But after a Korean Airlines jet with 269 passengers on board invading Soviet airspace was shot down in 1983, US President Ronald Reagan authorized partial use of the navigation system for civilian purposes. Notaccuracy was reduced by a special algorithm.

Then information appeared that some companies deciphered the algorithm for reducing accuracy and successfully compensated for this component of the error, and in 2000 this coarsening of accuracy was canceled by a decree of the President of the United States.

1. Satellite navigation system

Satellite navigation system- an integrated electronic-technical system, consisting of a combination of ground and space equipment, designed to determine the location (geographical coordinates and altitude), as well as movement parameters (speed and direction of movement, etc.) for ground, water and air objects.

1.1 What is GPS?

The GPS satellite navigation system was originally developed by the United States for military use. Another well-known name for the system is "NAVSTAR". The already household name "GPS" is an abbreviation for Global Positioning System, which translates as Global Navigation System. This name is fully characterized by the purpose of the system - providing navigation throughout the globe. Not only on land, but also at sea and in the air. Using the navigation signals of the GPS system, any user can determine their current location with high accuracy.

This accuracy is largely due to the steps taken by the US government in 2000 to make the GPS system available and open to civilian users. Recall that earlier with special treatment selective access (SA - Selective Availability), distortions were introduced into the transmitted signal, reducing the positioning accuracy to 70-100 meters. Since May 1, 2000, this mode has been disabled and the accuracy has increased to 3-10 meters.

In fact, this event gave a powerful impetus to the development of household GPS navigation equipment, reducing its cost, and actively popularizing it among ordinary users. Currently, GPS receivers different types are actively used in all areas of human activity, ranging from conventional navigation to personal control and exciting games, such as " Geocaching". According to the results of many studies, the use of GPS navigation systems has a great economic effect on the world economy and ecology - traffic safety increases, traffic situation improves, fuel consumption decreases, and the amount of harmful emissions into the atmosphere decreases.

The growing dependence of the European economy on the GPS system, and, as a result, on the US administration, forced Europe to start developing its own navigation system - Galilleo. New system in many ways similar to a GPS system.

2. Composition of the GPS system

2.1 Space segment

The space segment of the GPS system consists of an orbital constellation of satellites that emit navigation signals. The satellites are located in 6 orbits at an altitude of about 20,000 km. The period of revolution of the satellites is 12 hours and the speed is about 3 km/s. Thus, in a day, each satellite makes two complete revolutions around the Earth.

The first satellite was launched in February 1978. Its size with open solar panels was 5 meters, and weight - more than 900 kg. It was the satellite of the first modification of GPS-I. Over the past 30 years, several modifications of GPS satellites have changed in orbit: GPS II-A, GPS II-R, GPS IIR-M. In the process of modernization, the weight of the satellites was reduced, the stability of the on-board clock was improved, and reliability was increased.

GPS satellites transmit three navigation signals on two frequencies L1 and L2. The "civilian" C/A signal, transmitted on the L1 frequency (1575.42 MHz), is available to all users and provides positioning accuracy of 3-10 meters. A high-precision "military" P-code is transmitted at frequencies L1 and L2 (1227.60 MHz) and its accuracy is an order of magnitude higher than the "civilian" signal. The use of a signal transmitted at two different frequencies also makes it possible to partially compensate for ionospheric delays.

In the latest modification of the GPS IIR-M satellites, a new “civilian” L2C signal is implemented, designed to increase GPS accuracy measurements.

Identification of navigation signals is carried out by the number corresponding to the "pseudo-noise code", unique for each satellite. The technical specification of the GPS system originally contained 32 codes. At the stage of development of the system and the initial period of its operation, it was planned that the number of working satellites would not exceed 24. Free codes were allocated for new GPS satellites at the commissioning stage. And this amount was enough for the normal functioning of the system. But at present, there are already 32 satellites in orbit, of which 31 are in operation, transmitting a navigation signal to Earth.

The "redundancy" of satellites allows the user to calculate the position in conditions where the "visibility" of the sky is limited by high-rise buildings, trees or mountains.

2.2 Ground segment

The ground segment of the GPS system consists of 5 control stations and a main control station located at US military bases - on the islands of Kwajalein and Hawaii in the Pacific Ocean, on Ascension Island, on the island of Diego Garcia in the Indian Ocean and in Colorado Springs, they converted to figure 1.The tasks of monitoring stations include receiving and measuring navigation signals coming from GPS satellites, calculating various kinds of errors and transmitting these data to the control station. The joint processing of the received data makes it possible to calculate the deviation of the satellite trajectories from the given orbits, time shifts of the onboard clocks, and errors in navigation messages. Monitoring of the status of GPS satellites occurs almost continuously. The "download" of navigation data, consisting of predicted orbits and clock corrections for each of the satellites, is carried out every 24 hours, at the moment when it is in the control station's access zone.

In addition to terrestrial GPS stations, there are several private and public networks tracking, which perform measurements of GPS navigation signals to refine the parameters of the atmosphere and the trajectories of satellites.

Picture 1

2.3 User equipment

User equipment refers to navigation receivers that use the signal from GPS satellites to calculate the current position, speed and time. User equipment can be divided into "household" and "professional". In many ways, this division is conditional, since sometimes it is quite difficult to determine which category a GPS receiver should be assigned to and what criteria should be used. There is a whole class of GPS navigators used for hiking, car travel, fishing, etc. There are aviation and maritime navigation systems, which are often part of complex navigation systems. Recently, GPS chips have been widely used, which are integrated into PDAs, phones and other mobile devices.

Therefore, in navigation b O The division of GPS receivers into "code" and "phase" receivers has become more widespread. In the first case, information transmitted in navigation messages is used to calculate the position. This category includes most inexpensive GPS navigators, costing $ 100-2000.

The second category of GPS navigation receivers uses not only the data contained in the navigation messages, but also the phase of the carrier signal. In most cases, these are expensive single- and dual-frequency (L1 and L2) geodetic receivers capable of calculating a position with a relative accuracy of several centimeters or even millimeters. This accuracy is achieved in RTK mode, by jointly processing the measurements of the GPS receiver and data base station. The cost of such devices can be tens of thousands of dollars.

3. Work GPS Navigator A

The basic principle underlying the entire GPS system is simple and has long been used for navigation and orientation: if you know the exact location of any reference point and the distance to it, then you can draw a circle (in the 3-dimensional case, a sphere), on which the point of your position should be located. In practice, if the above distance, i.e. radius is large enough, then you can replace the arc of a circle with a straight line segment. If you draw several such lines corresponding to different reference points, then the point of their intersection will indicate your location. In GPS, the role of such benchmarks is played by two dozen satellites, each moving in its own orbit at an altitude of ~ 17,000 km above the Earth's surface. The speed of their movement is very high, however, the parameters of the orbit and their current location are known to on-board computers with high accuracy. An important part of any GPS navigator is a conventional receiver operating at a fixed frequency and constantly “listening” to the signals transmitted by these satellites. Each of the satellites constantly emits a radio signal, which contains data on the parameters of its orbit, the state of onboard equipment and the exact time. Of all this information, accurate on-board time data is the most important: the GPS receiver, using its built-in processor, calculates the time interval between sending and receiving a signal, then multiplies it by the speed of propagation of radio waves, and so on. finds out the distance between the satellite and the receiver.

Everyone, most likely, had to get into an unfamiliar area, where they had to orient themselves without wasting time. An excellent assistant in solving this problem will be a satellite GPS-navigator. Services of the global navigation system GPS are free of charge.

Systems operating via satellites have similar basic functions: finding the best route from one point to another, as well as laying a new route when deviating from the original one. Details may vary. For example, some devices have a voice prompt, display a map in 2D and 3D modes, and prompt information about road signs. Many of them have multimedia features. The effectiveness of the device will depend on the quality electronic card in his memory.

Three classes should be distinguished from the variety of satellite GPS navigators according to their purpose and design. The first includes embedded modules or compact devices that work via satellite to work together with other electronics - a computer or mobile phone. They don't have a display. Devices of the second class will display navigation information on the display screen, save it and plot the best route. The third class is GPS-equipment capable of processing cartographic information, downloaded or embedded.

In order not to make a mistake in choosing a satellite navigator, you should decide for what purposes it will be used. For pedestrian use, convenient one-handed devices are suitable, where the buttons are located on the side surfaces of the case. For auto the best option There will be a system with a large display. The yacht may be equipped with a device with an alarm function that is triggered when you deviate from the course or from the anchorage point.

For extreme conditions suitable satellite navigators that are protected from moisture, dust, shock, exposure to low and high temperatures. The price range is very wide and depends on the functionality of the system.

In addition to the advantages, the GPS-system has some disadvantages. Since the navigator receiver is a passive device, the satellite signal is so weak that it is sometimes difficult to determine your position. This can happen in a gorge, dense forest or tunnel. In this case, a remote antenna will help, which will connect only to those devices where there is a special socket. If necessary, you can also find a GPS navigator with a built-in electronic magnetic compass and an autonomous barometric altimeter. This will allow you to navigate the terrain in a classic way.

A navigation system is a set of devices that provide navigation (orientation) of an object in space. Navigation systems provide orientation using: maps that have video, graphic or text formats; location determination using sensors or other external sources; autonomous means, such as satellite connection and so on.; information from other entities. Satellite navigation system - a complex electronic-technical system, consisting of a combination of ground and space equipment, designed to determine the location (geographical coordinates and altitude), as well as movement parameters (speed and direction of movement, etc.) for ground, water and air objects. The main elements of the satellite navigation system:

• An orbital constellation consisting of several (from 2 to 30) satellites emitting special radio signals;
• Ground-based command and control system, including blocks for measuring the current position of satellites and transmitting the information received to them to correct information about orbits;
• Receiving client equipment ("satellite navigators") used to determine coordinates;
• Optional: ground system radio beacons, which can significantly improve the accuracy of determining coordinates.
• Optional: information radio system for transmitting corrections to users, which can significantly improve the accuracy of determining coordinates.

Russia ranks third in the number of communication satellites

As of the end of 2016, Russia ranks third in terms of the number of communication satellites, owning 17 spacecraft. The country is inferior in this indicator to France, which has twice as many satellites - 34, as well as to a small state - Luxembourg, which owns 108 devices. This was reported by TASS with reference to Nikolai Sevastyanov, general designer of Gazprom Space Systems. Japan has 16 communications satellites, followed by the United States and Hong Kong with 11 satellites in fifth place.

The volume of the world market of space communications, which has existed for 45 years, is $153 billion with an annual increase of 3%. The main part of it is TV, radio and the Internet - $104 billion. The segment of communication channels is estimated at $18 billion, mobile communications - at $3 billion.

What is GPS vehicle monitoring?

GPS monitoring of transport is a continuous tracking of the cars of your fleet. The vehicle monitoring system allows real-time GPS tracking. The GPS equipment installed on the vehicle requests its location from one of the GPS constellation satellites and transmits the information to the dispatcher online. Similar system GPS navigation made it possible to move from the level of simple control of the movement of vehicles to the level of full-fledged vehicle tracking.

When implementing a GPS / GLONASS vehicle monitoring system, in addition to tracking vehicles, constant monitoring of the fuel level, the condition of the car, its exact coordinates, the time during which the car was idle or in motion, and much more is carried out.

Since the signal is in real time, modern transport control systems perform much more features than just GPS monitoring of cars. Today, tracking the movement of vehicles, GPS equipment allows the dispatcher to quickly respond in case of emergency situations.

The dispatcher in the process of controlling the movement of transport can set voice communication with a driver, remotely turn off the car engine and much more. Such an expansion of transport monitoring capabilities allows not only to receive information about problems and violations that affect the company's transport costs, but also to quickly level them.

Installation of a GPS / GLONASS vehicle monitoring system for constant satellite control of vehicles

Today, the Russian navigation system based on GLONASS plays an important role in ensuring security at the state level. Modern system GLONASS monitoring of transport allows you to control transport using the Russian constellation of satellites. The creation of a constellation of satellites began in the 80s and includes about 27 satellites. The principle of operation of GLONASS monitoring satellites is similar to the American NAVSTAR GPS system. But, unlike it, it does not require any additional updates after launch.

Determining your location, both on land and at sea, in a forest or in a city, is an issue that is as relevant today as it has been over the past centuries. The era of the discovery of radio waves greatly simplified the task of navigation and opened up new prospects for humanity in many areas of life and activity, and with the discovery of the possibility of conquering outer space, a huge breakthrough was made in the field of determining the coordinates of the location of an object on Earth. To determine the coordinates, a satellite navigation system is used, which receives the necessary information from satellites located in orbit.

Now there are two global coordinate systems in the world - the Russian GLONASS and the American NavStar, better known as GPS (an abbreviation for the name Global Position System - global positioning system).

The GLONASS satellite navigation system was invented in the Soviet Union in the early 80s of the last century and the first tests took place in 1982. It was developed by order of the Ministry of Defense and was specialized for operational global navigation of ground moving objects.

The American GPS navigation system is similar in structure, purpose and functionality to GLONASS and was also developed by order of the United States Department of Defense. It has the ability to determine with high accuracy both the coordinates of a ground object, and to carry out time and speed binding. NavStar has 24 navigation satellites in orbit, providing a continuous navigation field over the entire surface of the Earth.

The receiver indicator of the satellite navigation system (GPS-navigator or) receives signals from satellites, measures the distances to them, and, using the measured ranges, solves the problem of determining its coordinates - latitude, longitude and, when receiving signals from 4 or more satellites - altitude above sea level , speed, direction (course), distance traveled. The navigator includes a receiver for receiving signals, a computer for their processing and navigation calculations, a display for displaying navigation and service information, and a keyboard for controlling the operation of the device.

These receivers are designed for permanent installation in wheelhouses and on dashboards. Their main features are: the presence of a remote antenna and power from an external source direct current. They have, as a rule, large liquid-crystal monochrome screens with alphanumeric and graphic display of information.

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Compact waterproof high performance GPS/DGPS/WAAS receiver designed for small boats. This GPS receiver from the company is capable of receiving and processing additional DGPS/WAAS differential correction signals. This feature allows, when receiving corrections from a beacon or geostationary WAAS satellites, to use an accuracy better than 5 meters.

New (D)GPS navigator with built-in differential correction receiver. Path-laying technology allows precise creation of long-range routes. It is possible to select loxodromic heading (RL) for short distances and orthodromic heading (GC) for long distances.

With pathfinding technology, it can accurately create high-range routes. It is possible to select loxodromic heading (RL) for short distances and orthodromic heading (GC) for long distances.

Fixed receivers have wide functionality, especially professional instruments for marine use. They have a large amount of memory, the ability to solve various navigational tasks, and their interface provides the ability to be included in the ship's navigation system.

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This is a modern GLONASS/GPS navigation satellite receiver designed for all types of ships.

Developed by specialists of the company "Radio Complex" using the latest achievements in the field of marine navigation. RK-2006 has the ability to receive signals from already deployed satellite constellations, such as GLONASS and GPS, but also from promising European and Asian positioning systems, this allows, with increased noise immunity and protection from the failure of any system, to determine the coordinates of the vessel and its course and speed.

The receiver of global navigation satellite systems GPS and GLONASS, from the South Korean manufacturer of marine radio navigation equipment Samyung ENC Co., Ltd - SGN-500.

When using GLONASS and GPS in combined receivers (almost all GLONASS receivers are combined), the accuracy of determining coordinates is almost always “excellent” due to a large number visible spacecraft and their good relative position.

Displaying navigation information

GLONASS/GPS receivers use two ways of displaying information: alphanumeric and graphic (sometimes the term "pseudographic" is used).

The alphanumeric method for displaying the information received uses:

• numbers (coordinates, speed, distance traveled, etc.)
• letter combinations that explain digital data are usually abbreviations of phrases (for example, MOV - "Man Over Board" or, in Russian - "Man overboard!"
• word abbreviations (for example, SPD - speed - speed, TRK - Track - route), waypoint names. Alphanumeric display of information in its purest form was used at the initial stage of the development of GPS technology.

The graphic display method is carried out with the help of drawings formed on the screen, representing the nature of the movement of the carrier (ship, car, person). The graphics in the devices of different companies are almost the same and differ, as a rule, in details. The most common drawings are:

• electronic compass (not to be confused with magnetic!)
• graphical movement indicator
• route, routes
• symbols for waypoints
• vessel coordinates
• direction to waypoint
• speed

Characteristics:

Location accuracy

The accuracy of determining the coordinates of a place is a fundamental indicator of any navigation system, the value of which will determine how correctly the ship will follow the route laid out and whether it will fall on nearby shoals or stones.

The accuracy of instruments is usually estimated by the value of the root-mean-square error (RMS) - the interval in which 72% of the measurements fall, or by the maximum error corresponding to 95%. Most manufacturers estimate the RMS of their GPS receivers at 25 meters, which corresponds to a maximum error of 50 meters.

Navigation performance

The navigation capabilities of GLONASS/GPS receivers are characterized by the number of waypoints, routes and waypoints contained in them that are memorized by the device. Waypoints are understood as characteristic points on the surface used for navigation. Modern ones can create and store, depending on the model, from 500 to 5000 waypoints and 20-50 routes with 20-30 points in each.

In addition to waypoints, any receiver has a reserve of points for recording and saving the route traveled. This number can reach from 1000 to several tens of thousands of points in professional navigators. The recorded track can be used to return along it.

Number of simultaneously tracked satellites

This indicator characterizes the stability of the navigator and its ability to provide the highest accuracy. Given the fact that to determine the two coordinates of the position - longitude and latitude - you need to simultaneously track 3 satellites, and to determine the height - four. Modern GLONASS/ GPS navigators, even wearable ones, have 8 or 12-channel receivers capable of simultaneously receiving and tracking signals of up to 8 or 12 satellites, respectively.

Many car owners use navigators in their cars. However, some of them are not aware of the existence of two different satellite systems - the Russian GLONASS and the American GPS. From this article you will learn what are their differences and which one should be preferred.

How the navigation system works

The navigation system is mainly used to determine the location of an object (in this case a car) and its speed. Sometimes it is also required to determine some other parameters, for example, height above sea level.

She calculates these parameters by setting the distance between the navigator itself and each of several satellites located in earth orbit. As a rule, for effective work system needs synchronization with four satellites. By changing these distances, it determines the coordinates of the object and other characteristics of the movement. GLONASS satellites are not synchronized with the rotation of the Earth, which ensures their stability over a long period of time.

Video: GlonaSS vs GPS

What is better GLONASS or GPS and what is their difference

Navigation systems primarily assumed their use for military purposes, and only then became available to ordinary citizens. Obviously, the military needs to use the developments of its own state, because a foreign navigation system can be turned off by the authorities of this country in the event of conflict situation. Moreover, in Russia they are calling for the use of the GLONASS system in everyday life by military and civil servants.

In everyday life, an ordinary motorist should not worry at all about the choice of a navigation system. Both GLONASS and provide navigation quality sufficient for everyday use. In the northern territories of Russia and other states located in northern latitudes, GLONASS satellites work more efficiently due to the fact that their trajectories are higher above the Earth. That is, in the Arctic, in the Scandinavian countries, GLONASS is more efficient, and the Swedes recognized this back in 2011. In other regions, GPS is slightly more accurate than GLONASS in determining location. According to Russian system differential correction and monitoring of GPS errors ranged from 2 to 8 meters, GLONASS errors from 4 to 8 meters. But GPS, to determine the location, you need to catch from 6 to 11 satellites, GLONASS is enough for 6-7 satellites.

It should also be noted that the GPS system appeared 8 years earlier and went into a solid gap in the 90s. And over the past decade, GLONASS has reduced this gap almost completely, and by 2020 the developers promise that GLONASS will not be inferior to GPS in anything.

Most modern systems are equipped with a combined system that supports both Russian satellite system, and American. It is these devices that are the most accurate and have the lowest error in determining the coordinates of the car. The stability of the received signals also increases, because such a device can “see” more satellites. On the other hand, the prices for such navigators are much higher than single-system counterparts. It is understandable - two chips are built into them, capable of receiving signals from each type of satellite.

Video: test of GPS and GPS + GLONASS receivers Redpower CarPad3

Thus, the most accurate and reliable navigators are dual-system devices. However, their advantages are associated with one significant drawback - cost. Therefore, when choosing, you need to think - is such high accuracy needed in everyday use? Also, for a simple car enthusiast, it is not very important which navigation system use - Russian or American. Neither GPS nor GLONASS will let you get lost and take you to your desired destination.