It is already impossible to imagine the modern world without a developed telecommunications sector. Just as you cannot force people to use kerosene lamps when there is electric light around, so you cannot force them to stop using the Internet, satellite TV and navigators. In this article, we will consider some issues related to global positioning satellite systems used for navigators, including car GPS and GLONASS. As a result, having learned a little about each of these systems, you can choose the best alternative for yourself when buying a car navigator.
About GPS and GLONASS satellite positioning systems
Although the era of the Great geographical discoveries has long passed, nevertheless, the problem of accurately determining the geographical coordinates of an object, moving or stationary, was a complex mathematical problem with many unknowns. The development of the space industry, the widespread use of artificial Earth satellites, first to transmit simple text information, then more and more complex and large information arrays, prompted scientists to develop systems for determining the ground coordinates of objects using artificial Earth satellites. Of course, the solution of this problem was not trivial either. But here computer technology came to the rescue, which greatly accelerated the processes of calculating and taking into account many parameters when determining the geographical coordinates of objects. The first customers of such systems were the military - where without them. They had to know exactly the location, at first only of nuclear facilities, both of the enemy and their own, missile-carrying aircraft, nuclear submarines, and now it has come to determining the location of each soldier on the battlefield.
But, this state of affairs could not last long, and already in the new millennium, the military was forced to open systems for civilian use. Household navigators were developed very quickly, including auto-umbilical ones, which showed your position in one place or another on the globe with sufficient accuracy. But, it must be said right away that the accuracy, determination of the coordinates of the positioning systems used in the civilian and military sectors differ, and quite strongly.
Global positioning systems have found applications in logistics, giving rise to its new direction - telematics. The second direction is global emergency warning systems. In addition, positioning systems are extremely important in geodesy, cartography, land management and other industries. Well, domestic use is navigators that can be used not only in a car, but also just walking around an unfamiliar city, etc.
At the moment, several global positioning systems have been developed. But three of them can be distinguished - This is the American GPS, the Russian GLONASS, the European Galileo. In addition, China and India are also developing their positioning systems so as not to depend on the Americans, who can reduce the accuracy of determining an object, or even turn off the broadcast of signals in certain areas. There have already been precedents.
About the GPS system for navigators
GPS stands for Global Positioning System, or in Russian - Global Positioning System. Like any positioning system, GPS consists of a space segment, which currently consists of more than thirty satellites, a system of ground command complexes that control the space segment, and, in fact, receivers located at consumers.
We will not go into the technical details of the functioning of systems, but simply talk about general concepts. The satellites rotate in six planes, at a distance of about 20,000 km from the Earth's surface. Satellites broadcast two types of signals: C/A code, which is a public signal, and P code, a protected code. The P-code is about 10 times more accurate than the public signal. Access to a signal with a P-code can be given by the US military department. This code has a high degree of encryption, so no one will open the cipher in vain.
How GPS works
The satellites included in the system constantly radiate a signal to the earth's surface. The navigator, in order to determine the point of its location, needs to calculate three coordinates and take into account the difference in the time scales of both the satellite and the navigator. As a rule, signals from four satellites are used for error compensation, although signals from more satellites can be used. Having captured the signal of the satellites, the navigator extracts the C\A sequence from it, compares it with its parameters and builds a three-dimensional picture relative to the satellites. This requires constant synchronization of the signal from the satellite. The measurement accuracy also depends on the location of the satellites from which the signal is received. If, for example, they are all in the northern and western segments, then it will be impossible to build a correct triangulation (a network of reference geodetic points).
About the GLONASS system for navigators
Unfortunately, the times of perestroika and the transition to a new economic formation delayed the development of such a system in our country. In general, we are now lagging behind in the development of the system. There are fewer satellites in the space segment, the software microprocessors that perform calculations are also not the most advanced. And besides, the moment was missed when the market demanded navigators, and our industry could not provide them to consumers. Therefore, in the course of the phrase jeepies navigator, and not glonass navigator.
Glonass satellites emit two frequencies. One is called the standard precision frequency, the second is the high precision frequency. As you understand, the second frequency serves the needs of the military and special services. The principle of operation of the system is the same, so we will not repeat ourselves.
GLONASS provides the following parameters: - accuracy in horizontal coordinates 50-70 meters - accuracy in vertical coordinates 70 meters - determination of the motion vector up to 15 cm/s Of course, these are the maximum error rates. Under favorable conditions, they can be 2-3 times better. The indicators are not worse than the American ones. For example, in GPS, the error in the accuracy of coordinates can reach 100 m. The satellites are located in three planes, at an angle of 120 degrees. Americans have 6 planes, with a shift of 60 degrees. GLONASS is more effective in high latitudes, where most of our country is located, GPS - in middle latitudes. Everyone created a system for themselves.
Which navigator is better than GPS or GLONASS?
The main thing that hinders the development and distribution of GLONASS navigators is poor cartographic support. Without clear, correctly drawn maps, a navigator is a useless toy. Unfortunately, mapping has always been the prerogative of the military, and has often been shrouded in a veil of secrecy. Now we are paying for it. Of course, there are some exceptions, but the bulk of the country's territory should be available on maps for civilian navigators. At the moment, this is the biggest problem for GLONASS navigators, which both hinders their implementation for civilians and makes them less attractive for general use. It remains to "look to the future" with hope, and hopes that even the civilian population of our country will not depend on well-coordinated work, but still American satellites.
Article about GLONASS and GPS systems: characteristics of satellite systems, their features and comparative analysis. At the end of the article - a video about the principles of GPS and GLONASS.
Now the spheres of influence are divided between the Russian GLONASS, the American GPS (Global Positioning System) and the Chinese BeiDou, which is gradually gaining momentum. The choice of a system for your own car may be patriotic, or it may be based on a competent weighing of the advantages and disadvantages of these developments.
Basics of satellite communications
The purpose of each satellite system is to determine the exact location of any object. In the context of a car, this task is carried out by means of a special device that helps to establish coordinates on the ground, known as a navigator. Satellites interacting with a particular navigation system send it personal signals that are different from each other. For a clear definition of spatial coordinates, the navigator needs information from 4 satellites. Thus, this is not a simple car gadget, but one of the elements of a complex space positioning mechanism.
When the car moves, the coordinates change continuously. Therefore, the navigation system is designed so that at some regular intervals to update the received data and recalculate the distance.
The advantage of modern systems is that they have the ability to remember the satellite layout even when turned off. This greatly increases the efficiency of the instrument when there is no need to re-search the satellite's orbit each time. For motorists who regularly access the navigator, the developers have provided a "hot start" function - the fastest possible connection of the device with the satellite. With rare use of the navigator, the start will be “cold”, that is, in this case, the connection with the satellite will be longer, taking from 10 to 20 minutes. Building systems
Although the first satellite of the Earth was a Soviet development, at first it was born precisely American GPS. Scientists drew attention to changes in satellite signals, depending on its movement in orbit. Then they thought about the method of calculating not only the coordinates of the satellite itself, but also the terrestrial objects tied to it. In 1964, an exclusively military navigation system called TRANZIT was launched, which became the world's first development of this level. She contributed to the launch of missiles from submarines, but the accuracy of the location of the object was calculated only at a distance of 50 meters. In addition, this object had to remain absolutely motionless.
It became clear that the first and at that time the only navigator in the world could not cope with the task of constantly determining the coordinates. This was due to the fact that, passing in low orbit, the satellite could only send signals to Earth for an hour.
The next, upgraded version appeared 3 years later, along with the new satellite Timation-1 and its brother Timation-2. Together they rose to a higher orbit and united into a single system, called Navstar. It started in the same way as a military development, but then it was decided to make it publicly available for the needs of the civilian population.
This system is still functioning, with 32 satellites in its arsenal, providing full coverage of the Earth. Another 8 devices are in reserve for some unforeseen event. Moving at a significant distance from the planet in several orbits, the satellites complete their revolution in almost a day.
Above domestic GLONASS system began to work in the days of the Union - a powerful state with outstanding scientific minds. The launch of an artificial satellite into orbit launched the design work of the positioning system.
The first Soviet satellite born in 1967 was supposed to be the only one sufficient to calculate the coordinates. But soon a whole system equipped with radio transmitters appeared in space, known to the population as the Cicada, the military called it the Cyclone. Her task was to identify objects in distress, which she did until the advent of GLONASS in 1982. The Soviet Union was destroyed, the country was in distress and could not find reserves to bring the high-tech system to mind. The whole system included 24 satellites, but due to financial difficulties, almost half of them did not function. Therefore, at that time, in the 90s, GLONASS could not even compete closely with GPS.
To date, Russian developers intend to overtake and overtake their American counterparts, which already confirms the faster circulation of our satellites around the Earth. Although historically the Russian satellite system lagged far behind the American one, this gap is shrinking from year to year.
Advantages and disadvantages
At what level are both systems now? Which of them should be preferred by an ordinary man in the street for his everyday tasks? By and large, many citizens do not care what kind of satellite navigation his equipment uses. Both of them are available without restrictions and charges to the entire civilian population, including for use in a car. From a technical point of view, the Swedish satellite company has officially announced the merits of GLONASS, which works much better in northern latitudes.
GPS satellites practically do not appear north of the 55th parallel, and in the southern hemisphere, respectively, to the south. Whereas with an inclination angle of 65 degrees and an altitude of 19.4 thousand km, GLONASS satellites deliver excellent, stable signals to Moscow, Norway and Sweden, which is so appreciated by foreign experts.
Although both systems have a large number of satellites in all orbital planes, other experts still give the palm to GPS. Even with an active program to improve the Russian system, at the moment the Americans have 27 satellites against 24 Russian ones, which makes their signals more clear.
The reliability of GLONASS signals is 2.8 m compared to 1.8 m for GPS. However, this figure is quite average, because satellites can line up in orbit in such a way that the error rate increases several times. Moreover, such a situation can comprehend both satellite systems.
For this reason, manufacturers are trying to equip their devices with dual-system navigation that receives both GPS and GLONASS signals.
An important role is played by the quality of ground equipment that receives and decrypts the received data.
If we talk about the identified shortcomings of both navigation systems, they can be distributed as follows: GLONASS:
- change of celestial coordinates (ephemeris) leads to inaccuracy in determining the coordinates, reaching 30 meters;
- quite frequent, albeit short-term interruption of the signal;
- tangible influence of relief features on the clarity of the data obtained.
GPS: - receiving an erroneous signal due to multipath interference and atmospheric instability;
- a significant difference between the civilian version of the system, which has too limited capabilities compared to the military development.
Two-system
In total, more than five dozen satellites of both world powers are constantly spinning in orbit. As already mentioned, a good “view” of 4 satellites is sufficient to obtain reliable coordinates. On a flat area, in the steppe or in the field, any receiver will be able to record up to a dozen signals simultaneously, while in a forest or mountainous area, communication is rapidly disappearing. Thus, the design goal is for each receiving device to be able to communicate with the maximum number of satellites. This again brings back the idea of combining GLONASS and GPS, which is already being practiced in America for rescue services. No matter how the relations of states develop, human life is above all, and the dual-system chip will determine the location of a person in trouble with greater speed and clarity.
Such a synthesis will also save motorists from being unable to navigate in unfamiliar areas due to the fact that the navigator is too slow to establish a connection and processes information for too long. The reason for this is the loss of a satellite due to banal interference: a tall building, overpass or even a large truck in the neighborhood. But if the autonavigator is equipped with a dual-system chip, the likelihood of its “freezing” will be significantly reduced.
When this practice becomes widespread, the navigator will be indifferent to the country of origin of the system, because it will be able to simultaneously track up to 40 satellites, giving a fantastically accurate location.
Video about the principles of GPS and GLONASS:
Now many of us cannot imagine our lives without any devices that were born with the help of the latest technologies. A striking example are all kinds of gadgets designed to calculate the location. They can be anti-theft devices, portable navigators, or even entire tracking systems. All of them have a number of features and differ from each other in a set of functions.
But the most important difference that a potential buyer most often pays attention to is the accuracy of determining the location coordinates.
All devices of this kind can be divided into three groups depending on the technology used in their operation - GPS, GPRS and GLONASS. Each type of device has a number of advantages and disadvantages.
For quite a long time, there have been disputes between lovers of satellite systems. Some believe that the Russian GLONASS system is the height of perfection, while others are sure that at the moment there is not a single technology that can compete with GPS. Is it so?
To give a correct answer to this question, it is necessary to delve a little into history. In the technology of determining the position using satellites lies the Doppler effect, which is known to every person from a high school physics course. The bottom line is that the frequency of the satellite signal depends on the distance at which it is from the Earth.
Do not forget that the GLONASS system is much younger than GPS. This is confirmed by historical dates. At the time of the launch of the first navigation system, there was a gap of eight years between GPS and GLONASS. However, our scientists and engineers have done a tremendous job, so now both systems are direct competitors. At the moment, the error in determining the location coordinates of Glonass is slightly larger than that of GPS. However, representatives of the domestic company promise that by 2020 they will be able to catch up and overtake GPS in many ways.
What is the difference between GPS and GLONASS
Devices operating using the GPS system are very picky about the presence of active satellites. For the most accurate determination of the coordinates, the device must catch signals from six to eleven. But it is enough for the Glonass navigator to have six or seven active satellites in order to determine the location with the same error.
What is more accurate GLONASS or GPS? Do not forget about those devices that have both systems on board. Their scores are among the best. Such "double" devices are slightly more expensive than conventional ones, so it is best to purchase them to increase efficiency.
How is GPS different from GPRS? There is another technology that makes it possible to determine the location. It is called GPRS. This abbreviation is well known to all users of the mobile Internet, because it was with its help that, until recently, access to the worldwide network was carried out.
The main difference between these two systems is that GPS receives signals from satellites, while GPRS uses Internet access. That is why beacons that use only GPRS technology for determination often give out data with a large error. It is also worth noting that such tracking systems are imperfect, as they often find themselves in coverage areas.
To increase the level of security, GPS follows. Its cost is not very different, but the level of efficiency is an order of magnitude higher. The gprs technology has taken root very well in GPS GLONASS systems. That is, the device receives location data using three technologies at once, which significantly reduces the error.
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