Information about the difference between the readings of standard odometers and satellite navigators.

The presence of discrepancies between the readings of the standard odometer and the GPS/GLONASS odometer data can give rise to conflict situations. This article is intended to clarify the main reasons for such discrepancies in instrument readings.

Odometer is a device for measuring the number of wheel revolutions. Using it, the distance traveled by a vehicle can be measured. The odometer converts the distance traveled into readings on the indicator. Typically, an odometer consists of a counter with an indicator and a sensor associated with wheel rotation. The visible part of the odometer is its indicator. The mechanical indicator contains a series of wheels (drums) with numbers on the dashboard of the car. Each wheel is divided into ten sectors, with a number written on each sector. As the distance traveled by the vehicle increases, the wheels rotate, forming a number indicating the distance traveled.

The meter can be mechanical, electromechanical or electronic, incl. based on on-board electronic computing technology. Each of the above types of devices has its own parameters and errors.

First of all, we note that on-board odometers of all types do not belong to the class of precision instruments. For each type of these devices, permissible errors are established. Here it is necessary to make important remarks: firstly, these errors are established only for the devices themselves; all design changes, as well as physical wear and tear of some vehicle components, are not included in this error; secondly, according to technical requirements, speedometers cannot underestimate readings, therefore and the odometer, which is structurally connected to the speedometer, also, as a rule, gives slightly but inflated readings.

A sports odometer without any calibration overestimates speed and distance by 3.5%, which is required according to the International Convention on Road Traffic and GOST 12936-82, GOST 1578-76, GOST 8.262-77. There are no such standards for ordinary odometers (they were never developed due to the lack of requirements for the accuracy of these devices).

The error of the standard speedometer is a value calculated experimentally at the car manufacturer. The size of errors of different types of odometers is described below.

The mechanical odometer has its own error of up to 5%. Depending on the operating conditions of the vehicle, wear of components and assemblies, and the use of non-standard spare parts, the total error of the device can reach 12%-15%.

Electromechanical odometers - based on the readings of an electronic pulse number meter from the speed sensor, i.e. The instrument readings are proportional to the number of pulses per unit time. These devices are somewhat more accurate than mechanical ones, but still, they have an error of 5-7%, because they only got rid of the weak points of the mechanics themselves (plays, vagaries of the cable, coil, return spring, etc.).

Fully electronic odometers are more advanced than electromechanical ones, due to an improved mechanism for controlling the rotation of the drive wheel. At the same time, the very principle of monitoring the distance traveled remains unchanged, and even the precise electronics depend on the condition of the vehicle’s chassis. The total error of these devices rarely exceeds 5% if additional calibration is carried out on the test section of the route (this procedure does not occur at the manufacturer).

In reality, the accuracy of measuring the distance traveled by a car with any odometer is influenced by a large number of external factors:

Wheel height. A difference in tread height of 1 cm, for example, will give a difference in mileage of 1.177 km per 60 km of car mileage. (it’s easy to check, armed with a calculator and geometry formulas from a high school course - let’s take the diameter of one wheel to be 1 m, the second - 1.02 m. The first will make 19.108 revolutions, the second - 18.733. Each revolution is 3.14 m, the difference is 1177 m). And we get this difference with only one centimeter! Therefore, the odometer on a car with worn tread will show a higher value compared to the period when the car was driving on new tires. It is also important to know what type of wheels the odometer is designed for; if you install a different type of wheels in diameter, then there will be completely different data on the speed and distance traveled relative to the real ones, since both the speedometer and odometer count the number of wheel revolutions and calculate with the data on the wheel diameter provided by the manufacturer .

Wheels differ in diameter: 315/70 and 315/80, for example, will immediately give a difference in diameter of 6.3 cm, with all the ensuing consequences and errors.

Loading the car - When the car is fully or excessively loaded, the tire bends differently, hence the diameter of the wheel changes and, accordingly, we have the error quality described above.
Tire pressure - a tire wears out differently at standard and abnormal pressure.

Sliding of wheels on the road - logically speaking, when slipping, sliding, or vice versa - braking on ice, the car either remains in place when the wheels rotate, or vice versa - moves when the wheels are stopped.

The vehicle monitoring system based on GPS/GLONASS navigation works as follows. The GPS/GLONASS module determines data about its location, and then, using mobile communications via the Internet, sends this data to the server, where it is stored, processed with electronic maps, and a picture of the vehicle’s movement is built. In this case, it does not matter at all how fast the car with the block moves. The basic principle of using the system is to determine location by measuring distances to an object from points with known coordinates - satellites. The distance is calculated by the delay time of signal propagation from its sending by the satellite to reception by the GPS/GLONASS receiver antenna. That is, to determine three-dimensional GPS/GLONASS coordinates, the receiver needs to know the distance to three satellites and the time of the GPS/GLONASS system. Thus, to determine the coordinates and altitude of the receiver, signals from at least four satellites are used.

The calculation of the resulting coordinates also plays an important role, which allows you to reduce possible inaccuracies and present an accurate picture of the vehicle’s movement. Taking into account the accuracy of the GPS/GLONASS navigation system itself, as well as various kinds of software mechanisms that allow us to cut out major errors, the error of the monitoring system generally does not exceed 4%. This makes it possible to adjust the vehicle mileage data as much as possible.

A common disadvantage of using any radio navigation system is that under certain conditions the signal may not reach the receiver, or may arrive with significant distortion or delay. For example, it is almost impossible to determine your exact location in a basement or tunnel. Since the operating frequency of GPS/GLONASS lies in the decimeter radio wave range, the level of signal reception from satellites can seriously deteriorate under dense foliage of trees or due to very heavy clouds. Normal reception of GPS/GLONASS signals can be impaired by interference from many terrestrial radio sources, as well as from magnetic storms. According to official data, the net error of the navigator itself is within 10-15 meters.

Errors in the GPS/GLONASS positioning system itself are also possible.

Modern satellite navigation technologies provide location determination with an accuracy of about 10-15 meters. In most cases, this is enough, however, in some cases more is required: say, an autonomous drone moving quite quickly over the earth’s surface will feel uncomfortable in a cloud of coordinates with meter errors.

To clarify satellite data, differential systems and RTK (real-time kinematics) technologies are used, but until recently, such devices were expensive and cumbersome. Recent advances in digital technology in the form of the Intel Edison microcomputer have helped solve this problem. So, meet: Reach - the first compact high-precision GPS receiver, very affordable, and, moreover, developed in Russia.

First, let's talk a little about the differential technologies that allow Reach to achieve such high results. They are well known and quite widely implemented. Differential navigation systems (DNSS) improve the location and speed accuracy of mobile users by providing measurement data or correction information from one or more base stations.

The coordinates of each base station are known with high accuracy, so the station's measurements serve to calibrate data from nearby receivers. The receiver can calculate the theoretical distance and propagation time of the signal between itself and each satellite. When these theoretical values ​​are compared with observational data, the differences represent errors in the received signals. Correction information (RTCM data) is obtained from these differences.

Accuracy of coordinate determination using Reach. Pay attention to the scale.

Corrective information can be obtained by the Reach device from two sources. Firstly, from a public network of base stations via the Internet using the NTRIP protocol (Networked Transport of RTCM via Internet Protocol), which implements the idea described above in relation to a global computer network. Secondly, with the help of the second Reach, which occupies a stationary position near the first and is thus a base station in terms of DNSS. The second option is preferable (DNSS accuracy drops significantly with increasing distance between the receiver and the BS) - it is no coincidence that as part of the crowdfunding campaign on the Indiegogo website, the creators of Reach offer the first position to buy a set of two devices.

The device specifications are shown in the table below. As you can see, the hardware consists of 3 parts: an Intel Edison computer running Linux OS and RTK software RTKLIB; U-blox NEO-M8T GPS receiver and Tallysman TW4721 antenna. Please note that the receiver supports all existing satellite systems: GPS, GLONASS, Beidou and QZSS. This entire set of software and hardware components provides impressive accuracy in determining coordinates: up to 2 cm!
Who can use such a device? As mentioned above, the creators of various mobile robotics, autonomous and not so; Moreover, given its low cost (pre-order $545 for a double set and $285 for a single set), it will appeal not only to professionals, but also to enthusiasts. Further, compilers of various kinds of maps, again, including amateurs. Well, just nerds who want to know their location down to the centimeter.

The creators of Reach, the company Emlid, performed successfully on the indiegogo website: in less than a month, almost double the requested amount was collected. This means that the project will certainly be implemented. You still have time to pre-order and be among the first to receive a completely new navigation device. Distribution of goods is scheduled for July.

The user of a GPS navigator is always interested in the real accuracy of GPS navigation and the degree of confidence in its readings. How close can you get to any navigational hazard relying solely on your GPS receiver? Unfortunately, there is no clear answer to this question. This is due to the statistical nature of GPS navigation errors. Let's take a closer look at them.

The speed of propagation of radio waves is influenced by the ionosphere and troposphere, ionospheric and tropospheric refraction. This is the main source of errors after turning off SA. The speed of radio waves in vacuum is constant, but changes when the signal enters the atmosphere. The time delay is different for signals from different satellites. Radio wave propagation delays depend on the state of the atmosphere and the satellite's altitude above the horizon. The lower , the longer the path its signal travels through the atmosphere and the greater the distortion. Most receivers exclude signals from satellites with an elevation of less than 7.5 degrees above the horizon.

In addition, atmospheric interference depends on the time of day. After sunset, the density of the ionosphere and its influence on radio signals decreases, a phenomenon well known to shortwave radio operators. Military and civilian GPS receivers can autonomously determine atmospheric signal delay by comparing delays at different frequencies. Single-frequency consumer receivers make an approximate correction based on the forecast transmitted as part of the navigation message. The quality of this information has recently increased, which has further increased the accuracy of GPS navigation.

SA mode.

To maintain the advantage of high accuracy for military GPS navigators, the SA (Selective Availability) access restriction mode was introduced in March 1990, artificially reducing the accuracy of a civilian GPS navigator. When the SA mode is enabled, an error of several tens of meters is added in peacetime. In special cases, errors of hundreds of meters may be introduced. The US government is responsible for the performance of the GPS system to millions of users, and it can be assumed that the re-enablement of SA, much less such a significant reduction in accuracy, will not be introduced without sufficiently serious reasons.

Precision coarsening is achieved by chaotic shifting the transmission time of the pseudo-random code. Errors arising from SA are random and equally probable in each direction. SA also affects the GPS heading and speed accuracy. For this reason, a stationary receiver will often show slightly varying speed and heading. So the degree of impact of SA can be assessed by periodic changes in course and speed according to GPS.

Errors in ephemeris data during GPS navigation.

First of all, these are errors associated with the deviation of the satellite from the calculated orbit, clock inaccuracies, and signal delays in electronic circuits. These data are corrected from the Earth periodically, and errors accumulate in the intervals between communication sessions. Due to its small size, this group of errors is not significant for civilian users.

Extremely rare, larger errors may occur due to sudden information failures in the satellite's memory devices. If such a failure is not detected by self-diagnosis, then until the ground service detects the error and transmits a command about the failure, the satellite may transmit incorrect information for some time. There is a so-called violation of continuity or, as the term integrity is often translated, the integrity of navigation.

The influence of the reflected signal on the accuracy of GPS navigation.

In addition to the direct signal from the satellite, the GPS receiver can also receive signals reflected from rocks, buildings, passing ships - the so-called multipath propagation. If the direct signal is blocked from the receiver by the ship's superstructure or rigging, the reflected signal may be stronger. This signal travels a longer path, and the receiver “thinks” it is further from the satellite than it actually is. As a rule, these errors are much less than 100 meters, since only nearby objects can produce a strong enough echo.

Satellite geometry for GPS navigation.

Depends on the location of the receiver relative to the satellites by which the position is determined. If the receiver has picked up four satellites and they are all in the north, the satellite geometry is bad. The result is an error of up to 50-100 meters or even the inability to determine coordinates.

All four dimensions are from the same direction, and the area where the position lines intersect is too large. But if 4 satellites are located evenly on the sides of the horizon, then the accuracy will increase significantly. Satellite geometry is measured by the geometric factor PDOP (Position Dilution Of Precision). The ideal satellite location corresponds to PDOP = 1. Large values ​​indicate poor satellite geometry.

PDOP values ​​less than 6.0 are considered suitable for navigation. In 2D navigation, HDOP (Horizontal Dilution Of Precision) is used, less than 4.0. A vertical geometric factor VDOP less than 4.5 and a temporal TDOP less than 2.0 are also used. PDOP serves as a multiplier to account for errors from other sources. Each pseudo-range measured by the receiver has its own error, depending on atmospheric interference, errors in ephemeris, SA mode, reflected signal, and so on.

So, if the expected values ​​of the total signal delays for these reasons, URE - User Range Error or UERE - User Equivalent Range Error, in Russian EDP - equivalent rangefinder error, total 20 meters and HDOP = 1.5, then the expected determination error space will be equal to 20 x 1.5 = 30 meters. GPS receivers present information differently to evaluate accuracy using PDOP.

In addition to PDOP or HDOP, GQ (Geometric Quality) is used - the inverse value of HDOP, or a qualitative assessment in points. Many modern receivers display EPE (Estimated Position Error) directly in distance units. EPE takes into account the location of the satellites and the forecast of signal errors for each satellite depending on SA, the state of the atmosphere, and satellite clock errors transmitted as part of the ephemeris information.

Satellite geometry also becomes an issue when using the GPS receiver inside vehicles, in dense forests, mountains, or near tall buildings. When signals from individual satellites are blocked, the position of the remaining satellites will determine how accurate the GPS position will be, and their number will indicate whether the position can be determined at all. A good GPS receiver will show you not only which satellites are in use, but also their location, azimuth and elevation, so you can determine if a given satellite is having difficulty receiving.

Based on materials from the book “All about GPS navigators.”
Naiman V.S., Samoilov A.E., Ilyin N.R., Sheinis A.I.

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On approval of requirements for accuracy and methods for determining the coordinates of characteristic points of the boundaries of a land plot, as well as characteristic points of the contour of a building, structure or object of unfinished construction on a land plot

Pursuant to Part 7 of Article 38 and Part 10 of Article 41 of the Federal Law of July 24, 2007 No. 221-FZ “On the State Real Estate Cadastre” (Collected Legislation of the Russian Federation, 2007,
No. 31, art. 4017; 2008, No. 30, Art. 3597, art. 3616; 2009, No. 1, art. 19; No. 19, art. 2283; No. 29, art. 3582; No. 52, art. 6410, art. 6419) order:

approve the attached requirements for the accuracy and methods of determining the coordinates of characteristic points of the boundaries of a land plot, as well as characteristic points of the contour of a building, structure or unfinished construction site on a land plot.

Minister E.S. Nabiullina

Approved

by order of the Ministry of Economic Development of Russia

from___________ No.___________

Requirements for the accuracy and methods of determining the coordinates of characteristic points of the boundaries of a land plot, as well as characteristic points of the contour of a building, structure or object of unfinished construction on a land plot

1. A characteristic point of the boundary of a land plot is the point at which the description of the boundary of the land plot changes and its division into parts.

A characteristic point of the contour of a building, structure or unfinished construction object on a land plot is the point at which the boundary of the contour of a building, structure or unfinished construction object changes its direction.

2. The location on the ground of characteristic points of the border of a land plot is described by their flat rectangular coordinates in the Gauss-Kruger projection, calculated in the coordinate system adopted for maintaining the state real estate cadastre.

The location of a building, structure or object of unfinished construction on a land plot is established by determining flat rectangular coordinates in the Gauss-Kruger projection of characteristic points of the contour of such a building, structure or object of unfinished construction in the coordinate system adopted for maintaining the state real estate cadastre.

3. The coordinates of characteristic points of the boundaries of land plots and characteristic points of the boundaries of the contour of a building, structure or object of unfinished construction on a land plot are determined by the following methods:

1) geodetic method (method of triangulation, polygonometry, trilateration, method of direct, back or combined serifs and other geodetic methods);

2) by the method of satellite geodetic measurements (determinations);

3) photogrammetric method;

4) cartometric method.

4. The identification of characteristic points of the border of a land plot on the ground with boundary signs is carried out at the request of the customer of cadastral work. The design of the boundary sign is determined by the contract. In the case of fixing characteristic points of the boundary of a land plot with boundary signs, their coordinates refer to the fixed (designated) centers of boundary signs.

5. The method of work to determine the coordinates of characteristic points is established by the cadastral engineer depending on the available initial information and the requirements for the accuracy of determining the coordinates of characteristic points adopted in this document.

6. The geodetic basis for determining the flat rectangular coordinates of characteristic points of the border of a land plot are points of the state geodetic network and points of reference boundary networks.

The geodetic basis for determining the flat rectangular coordinates of the characteristic points of the contour of a building, structure or object of unfinished construction are the characteristic points of the border of the land plot.

The SKP location of a characteristic point of the contour of a building, structure or object of unfinished construction is determined relative to the nearest characteristic point of the boundary of the land plot.

7. The SKP location of the characteristic point of the border of the land plot should not exceed the standard accuracy of determining the coordinates of the characteristic points of the boundaries of the land plots (Appendix No. 1).

8. The SKP location of a characteristic point of the contour of a building, structure or object of unfinished construction should not exceed the standard accuracy of determining the coordinates of characteristic points of the contour of a building, structure or object of unfinished construction:

for lands of settlements – 1m;

for other lands – 5 m.

If the contour of a building, structure or unfinished construction object coincides with the boundary of a land plot, then the coordinates of the characteristic points of the contour of the building, structure or unfinished construction object are determined with the standard accuracy of determining the coordinates of the characteristic points of the boundaries of land plots.

If a building, structure or unfinished construction object is located on several land plots for which different standard accuracy is established, then the coordinates of the characteristic points of the outline of the building, structure or unfinished construction object are determined with an accuracy corresponding to the accuracy of determining the coordinates of the characteristic points of the outline of the building, structure or unfinished object construction with higher precision.

9. To determine the UPC location of a characteristic point, formulas are used that correspond to the methods for determining the coordinates of characteristic points.

10. Geodetic methods.

Calculation of the SCP location of characteristic points is carried out using software through which field materials are processed. In this case, a statement (extract) from the software is attached to the boundary plan.

When processing field materials without the use of software to determine the UPC location of a characteristic point, formulas for calculating the UPC are used that correspond to geodetic methods for determining the coordinates of characteristic points.

11. Method of satellite geodetic measurements.

Calculation of the SCP location of characteristic points is carried out using software through which satellite observation materials are processed. In this case, a statement (extract) from the software is attached to the boundary plan.

12. Cartometric and photogrammetric methods.

When determining the location of characteristic points combined with the contours of geographical objects depicted on a map (plan) or aerial photograph, the SKP is taken to be equal to Mt = K*M.

Where M is the denominator of the map or aerial photograph scale.

— for the photogrammetric method, K is taken equal to the graphic accuracy (for example, when determining the location of characteristic points from photographs - 0.0001 m);

— for the cartometric method:

— for populated areas K is taken equal to 0.0005 m;

- for agricultural and other lands
K is taken equal to 0.0007 m.

13. When restoring the boundary of a land plot on the ground based on information from the state real estate cadastre, the position of the characteristic points of the boundary of the land plot is determined with standard accuracy corresponding to the data presented in Appendix No. 1.

14. If adjacent land plots have different categories, then the common characteristic points of the boundaries of the land plots are determined with an accuracy corresponding to the accuracy of determining the coordinates of the land plot with higher accuracy.

15. At the request of the customer, the contract for cadastral work may provide for determining the location of characteristic points of the boundaries of the land plot and the contours of buildings, structures or unfinished construction objects with higher accuracy than established by this procedure. In this case, the determination of the coordinates of characteristic points of the boundaries of the land plot, the contours of buildings, structures or unfinished objects is carried out with the accuracy specified in the contract.

16. Based on the calculated coordinates of the characteristic points of the border of the land plot, a catalog of them is compiled, on the basis of which the area of ​​the land plot is calculated.

17. To calculate the maximum error in determining the area of ​​a land plot, the formula is used:

∆Р — maximum error in determining the area of ​​a land plot (sq.m);

M t — the maximum value of the mean square error of the location of characteristic points of the border of the land plot, calculated taking into account the technology and accuracy of the work (m);

R - land area (sq.m);

k— coefficient of elongation of the land plot, i.e. the ratio of the greatest length of a section to its smallest width.

Appendix No. 1

Standard accuracy of determining the coordinates of characteristic points of land boundaries

Item no.	Category of land, area of ​​land plots	Mean square error, (m)
1.	Agricultural land
	land area up to 1 hectare	0,2
	land area up to 100 hectares
	land area more than 100 hectares	2,5
2.	Lands of settlements	0,2
3.	Lands of industry, energy, transport, communications, radio broadcasting, television, computer science, lands supporting space activities, lands of defense, security and lands of other special purposes	0,5
4.	Lands of specially protected natural territories and objects, lands of the forest fund, lands of the water fund and reserve lands	5,0

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Testing the accuracy of GPS receivers for mobile phones

During work on one project, we needed to find out the real (and not declared) accuracy of geopositioning for various smartphones.

For this purpose, a stationary receiver from Topcon was used, the readings of which were taken as a standard. The tested devices were located in the same place. After a cold start, an additional 2 minutes were kept for a more accurate determination of the coordinates.

The following devices took part in testing:

• Fly IQ447 ($80);
• Nokia Lumia 625 ($100);
• Samsung Galaxy Tab 2;
• Industrial smartphone Motorola TC-55 – ($1500);
• Industrial smartphone Coppernic C-One ($1500);

It looked like this:

As a result, the results (the discrepancy between the coordinates of smartphones and the coordinates of a stationary receiver) were as follows:

• Fly IQ447 (GPS) – 1-3 meters;
• Coppernic C-One (GPS + GLONASS) – 2 meters;
• Motorola TC-55 (GPS + GLONASS) – 6 meters;
• Samsung Galaxy Tab 2 (GPS) – 8 meters;
• Nokia Lumia 625 (GPS) – 30 meters.

Motorola was a bit disappointed - for its price the results were expected to be better.

But what surprised me the most was the Fly phone. For its price of 3,000 rubles, it turned out to be the most accurate; despite the fact that it does not have a Glonass receiver. We rechecked the results several times, but they always turned out to be excellent.

By the way, this phone is the only one that always and everywhere on an airplane from a cold start finds satellites and calculates coordinates. Despite seemingly good reception conditions, most other phones do not always find a signal from a sufficient number of satellites in flight - sometimes you can wait 20 minutes, but still not be able to determine the coordinates.

By the way, we initially did not want to take the coordinates of a point on a map (for example, Yandex) as a standard. We are aware of the possible discrepancies between maps and real coordinates. At our point at Yandex, the magnitude of this discrepancy was about 5 meters.

Satellite positioning and navigation systems, originally developed for military needs, have recently found wide application in the civilian sphere. GPS/GLONASS monitoring of transport, monitoring people in need of care, monitoring the movements of employees, tracking animals, tracking luggage, geodesy and cartography are the main areas of use of satellite technologies.

Currently, there are two global satellite positioning systems created in the USA and the Russian Federation, and two regional ones, covering China, the countries of the European Union and a number of other countries in Europe and Asia. GLONASS monitoring and GPS monitoring are available in Russia.

GPS and GLONASS systems

GPS (Global Position System) is a satellite system whose development began in America in 1977. By 1993, the program was deployed, and by July 1995, the system was fully ready. Currently, the GPS space network consists of 32 satellites: 24 main, 6 backup. They orbit the Earth in a medium-high orbit (20,180 km) in six planes, with four main satellites in each.

On the ground there is a main control station and ten tracking stations, three of which transmit correction data to the latest generation satellites, which distribute them to the entire network.

The development of the GLONASS (Global Navigation Satellite System) system began in the USSR in 1982. The completion of the work was announced in December 2015. GLONASS requires 24 satellites to operate, 18 are sufficient to cover the territory and the Russian Federation, and the total number of satellites currently in orbit (including backups) is 27. They also move in a medium-high orbit, but at a lower altitude (19,140 km), in three planes, with eight main satellites in each.

GLONASS ground stations are located in Russia (14), Antarctica and Brazil (one each), and a number of additional stations are planned to be deployed.

The predecessor to GPS was the Transit system, developed in 1964 to control the launch of missiles from submarines. It could locate exclusively stationary objects with an accuracy of 50 m, and the only satellite was in the field of view for only one hour a day. The GPS program was previously called DNSS and NAVSTAR. In the USSR, the creation of a navigation satellite system began in 1967 as part of the Cyclone program.

The main differences between GLONASS and GPS monitoring systems:

• American satellites move synchronously with the Earth, while Russian satellites move asynchronously;
• different heights and number of orbits;
• their different angles of inclination (about 55° for GPS, 64.8° for GLONASS);
• different signal formats and operating frequencies.

Benefits of GPS

• GPS is the oldest existing positioning system; it was fully operational before the Russian one.
• Reliability comes from using a larger number of redundant satellites.
• Positioning occurs with a smaller error than GLONASS (on average 4 m, and for the latest generation satellites - 60–90 cm).
• Many devices support the system.

Advantages of the GLONASS system

• The position of asynchronous satellites in orbit is more stable, which makes them easier to control. Regular adjustments are not required. This advantage is important for specialists, not consumers.
• The system was created in Russia, therefore it ensures reliable signal reception and positioning accuracy in northern latitudes. This is achieved due to the greater angle of inclination of satellite orbits.
• GLONASS is a domestic system and will remain available to Russians if GPS is turned off.

Disadvantages of the GPS system

• Satellites rotate synchronously with the rotation of the Earth, so accurate positioning requires the operation of corrective stations.
• A low tilt angle does not provide a good signal and accurate positioning in polar regions and high latitudes.
• The right to control the system belongs to the military, and they can distort the signal or completely disable GPS for civilians or for other countries in the event of a conflict with them. Therefore, although GPS for transport is more accurate and convenient, GLONASS is more reliable.

Disadvantages of the GLONASS system

• The development of the system began later and until recently was carried out with a significant lag behind the Americans (crisis, financial abuse, theft).
• Incomplete set of satellites. The service life of Russian satellites is shorter than that of American satellites, they require repair more often, so the accuracy of navigation in a number of areas is reduced.
• GLONASS satellite vehicle monitoring is more expensive than GPS due to the high cost of devices adapted to work with the domestic positioning system.
• Lack of software for smartphones and PDAs. GLONASS modules were designed for navigators. For compact portable devices today, the more common and affordable option is support for GPS-GLONASS or GPS only.

Resume

GPS and GLONASS systems are complementary. The optimal solution is satellite GPS-GLONASS monitoring. Devices with two systems, for example, GPS markers with the M-Plata GLONASS module, provide high positioning accuracy and reliable operation. If for positioning exclusively using GLONASS the error averages 6 m, and for GPS – 4 m, then when using two systems simultaneously it decreases to 1.5 m. But such devices with two microchips are more expensive.

GLONASS was developed specifically for Russian latitudes and is potentially capable of providing high accuracy; due to its understaffing with satellites, the real advantage is still on the side of GPS. The advantages of the American system are the availability and wide selection of GPS-enabled devices.