Glonass system accuracy. Accuracy of coordinate determination in GPS navigation and causes of GPS errors
Many car owners use navigators in their cars. However, some of them do not know about the existence of two different satellite systems - the Russian GLONASS and the American GPS. From this article you will learn what their differences are and which one should be preferred.
How does the navigation system work?
The navigation system is mainly used to determine the location of an object (in this case a car) and its speed. Sometimes it is required to determine some other parameters, for example, altitude above sea level.
It calculates these parameters by establishing the distance between the navigator itself and each of several satellites located in Earth orbit. Typically, synchronization with four satellites is required for the system to operate effectively. By changing these distances, it determines the coordinates of the object and other characteristics of 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 were primarily intended to be used for military purposes, and only then became available to ordinary citizens. Obviously, the military needs to use the developments of their state, because a foreign navigation system can be turned off by the authorities of that country in the event of a conflict situation. Moreover, in Russia military and civil servants are encouraged to use the GLONASS system in everyday life.
In everyday life, an ordinary motorist should not worry at all about choosing a navigation system. Both GLONASS and provide navigation quality sufficient for everyday use. In the northern territories of Russia and other countries located at northern latitudes, GLONASS satellites work more efficiently due to the fact that their travel trajectories are higher above the Earth. That is, in the Arctic, in the Scandinavian countries, GLONASS is more effective, and the Swedes recognized this back in 2011. In other regions, GPS is slightly more accurate than GLONASS in determining location. According to the Russian system of differential correction and monitoring, GPS errors ranged from 2 to 8 meters, GLONASS errors from 4 to 8 meters. But for 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 taken into account that the GPS system appeared 8 years earlier and took a significant lead in the 90s. And over the last decade, GLONASS has reduced this gap almost completely, and by 2020, the developers promise that GLONASS will not be inferior to GPS in any way.
Most modern ones are equipped with a combined system that supports both the Russian satellite system and the American one. It is these devices that are the most accurate and have the lowest error in determining the vehicle’s coordinates. The stability of 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 their single-system counterparts. This 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 necessary in everyday use? Also, for a simple car enthusiast, it is not very important which navigation system to use - Russian or American. Neither GPS nor GLONASS will let you get lost and will take you to your desired destination.
Search Lectures
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.
Hello!
Unfortunately, I did not find any mention on Habré of a wonderful library for processing raw measurements - RTKLib. In this regard, I took the risk of writing a little about how you can use it to get centimeters in relative navigation.
The goal is simple - to attract public attention.
I myself only recently started working with this library and was amazed at its capabilities for mere mortals. There is a lot of information on practical examples on the Internet, but I wanted to try it myself - and here is the result.
So, the process in general looks like this:
Let's say we have two GLONASS/GPS receivers from which we can receive raw measurements. They are called raw because they are the primary material for processing - pseudo-ranges, Doppler, phase measurements...
Using the STRSVR utility from the RTKLib library, we need to record two data streams - one from the base station, which will stand still, and the second from the rover, which we plan to move. It is advisable to start recording from the base in advance, 10-15 minutes before recording the rover.
In my case, the base was on the roof of a building, and with the rover it went out onto the street. I used two laptops for recording.
1) Set up Input – Serial on both laptops, this is the stream from the GNSS receiver.
2) Output – File, this will be our file of raw measurements.
3) We start the base for recording – Start and slowly go to the open area.
For a small demonstration, I printed out an A4 sheet with the letter H, which I wanted to outline with the antenna, or rather with the base for mounting on a tripod. Antenna TW3440 manufactured by the Canadian company Tallysman with a custom underlying surface of 30x30 cm.
4) We position ourselves on the pavement, set the rover to record and try to slowly circle the letter. Even though the rover has an output frequency of 5Hz, it’s better to do everything carefully.
5) Upon completion of the stroke, we fold up and go see what happened.
6) We drop both files onto one computer and begin processing.
7) First, you need to obtain standard RINEX files from the raw data. RTKCONV will help us with this:
8) We indicate the path to the file with raw data, as well as the folder where the program will place RINEX, the raw data format, in my case it is NVS BINR and in the settings we check the GPS and GLO boxes, the rest can be left untouched.
9) Click Convert and get files for the rover and then for the base; it is better to place them in the corresponding Base and Rover folders.
11) Click Options, Settings 1 tab, in the mode settings we specify Kinematic to process relative measurements. We tick the GPS and GLO boxes, then you can play with the settings.
12) Output tab – you can set the output data format, for example NMEA.
13) An important point is the Positions tab, here you need to indicate the coordinates of the base station, either take them from the header, or by averaging over the recording period. The more accurately we know the coordinates of the base, the more accurate the absolute coordinates of the rover will be.
For example, let's indicate RINEX Header Position - taken from the file header.
14) Click OK and go to the main window, there in the Rover field we indicate the path to the RINEX file of the rover, and for the database the path to the corresponding file. Click Execute and wait for the result. After processing, we can see the result by clicking on Plot.
15) From the figure below you can see that 97.3% of solutions with centimeter accuracy were obtained, the rest is a floating solution, the accuracy of which is much worse.
That's all for now.
If anyone is interested, I can write how to implement RTK mode.
It would also be nice to know your opinion: in what non-obvious applications can solutions with centimeter navigation be used?
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.
Purpose
GPS (Global Positioning System) allows you to accurately determine the three-dimensional coordinates of an object equipped with a GPS receiver: latitude, longitude, altitude above sea level, as well as its speed, direction of movement and current time.
Brief history
The GPS system was developed by the US Department of Defense. Work on this project, called NAVSTAR (NAVigation System with Timing and Ranging - navigation system for determining time and range), began back in the 70s. The first satellite of the system was launched into orbit in 1974, and the last of the 24 needed to cover the entire Earth only in 1993. Initially, GPS was intended for use by the US military (navigation, missile guidance, etc.), but since 1983, when it was shot down a Korean Airlines plane accidentally intruded into Soviet territory, the use of GPS was allowed for civilians. At the same time, the accuracy of the transmitted signal was coarsened using a special algorithm, but in 2000 this limitation was lifted. The US Department of Defense continues to maintain and upgrade the GPS system. It was this complete dependence of the system's performance on the government of one country (for example, during the first Gulf War, the civilian GPS sector was turned off) that prompted other countries to develop alternative navigation systems (Russian - GLONASS, European - GALILEO, Chinese - Beidou).
Principles of determining coordinates
The principle of determining the coordinates of an object in the GPS system is based on calculating the distance from it to several satellites, the exact coordinates of which are known. Information about the distance to at least 3 satellites allows you to determine the coordinates of an object as the point of intersection of spheres, the center of which is the satellites, and the radius is the measured distance.
In fact, there are two points of intersection of the spheres, but one of them can be discarded because it is either deep inside the Earth or very high above its surface. The distance to each satellite is defined as the time it takes for a radio signal to travel from the satellite to the receiver multiplied by the speed of light. The problem arises of accurately determining the transit time of a radio signal. It is solved by generating and transmitting a signal from the satellite, modulated using a special sequence. Exactly the same signal is generated in the GPS receiver, and analysis of the lag of the received signal from the internal signal makes it possible to determine its travel time.
To accurately determine the signal travel time, the clocks of the GPS receiver and satellite must be synchronized as much as possible; a deviation of even a few microseconds leads to a measurement error of tens of kilometers. The satellite has high-precision atomic clocks for these purposes. It is impossible to install a similar clock in a GPS receiver (regular quartz clocks are used), so additional signals from at least one more satellite are used to synchronize time. It is assumed that if the time in the GPS receiver is precisely synchronized, then a circle with a radius equal to the distance from the fourth satellite will intersect the same point as the circles from the other three satellites. The GPS receiver adjusts its clock until this condition is met. Thus, to accurately determine the position of an object in three-dimensional space (3D), signals from at least 4 satellites are required (from 3 satellites without determining the height above the earth’s surface - 2D). In practice, with good visibility of the sky, GPS receivers receive signals from many satellites at once (up to 10-12), which allows them to synchronize clocks and determine coordinates with fairly high accuracy.
Along with the sequence by which the signal propagation time is determined, each satellite transmits binary information - an almanac and ephemeris. The almanac contains information about the current state and estimated orbit of all satellites (having received information from one satellite, it becomes possible to narrow the search sectors for signals from other satellites). Ephemeris - updated information about the orbit of a specific satellite transmitting a signal (the actual orbit of the satellite may differ from the calculated one). It is the exact data about the current position of the satellites that allows the GPS receiver to calculate its own location relative to them.
GPS Accuracy
The typical accuracy of determining coordinates by GPS receivers in the horizontal plane is approximately 1-2 meters (provided good visibility of the sky). The accuracy of determining altitude above sea level is usually 2-5 times lower than the accuracy of determining coordinates under the same conditions (i.e., in ideal conditions, 2-10 meters).
The level of signal reception from satellites, and as a result the accuracy of determining coordinates, deteriorates under dense foliage of trees or due to very heavy clouds. Also, normal reception of GPS signals can be impaired by interference from many terrestrial radio sources. However, the main factor influencing the decrease in GPS accuracy is incomplete visibility of the sky. This is especially evident when the GPS receiver is located in dense urban areas, when a significant part of the sky is hidden by nearby buildings, canopies and other obstacles. The accuracy of determining coordinates can drop to 20-30 meters, and sometimes more. Obstacles do not allow signals from some satellites potentially available at a given point on the Earth to pass through. This leads to the fact that calculations are carried out using a smaller number of signals from satellites located primarily in one sector of the sky. The displacement usually occurs in a plane perpendicular to the obstacle.
In general, if we talk about the accuracy of GPS in urban conditions, based on accumulated statistical data and our own experience, we can draw the following conclusions. The accuracy of determining coordinates when the vehicle is in an open area (parking lot, square, etc.) and when driving along major highways and multi-lane roads will be 1-2 meters. When driving along narrow streets, especially when there are closely spaced houses along them, the accuracy will be 4-10 meters. When the car is in “yard wells”, very close to high-rise buildings, etc. accuracy can drop down to 20-30 meters.
Of course, the accuracy of determining coordinates greatly depends on the quality of the GPS receiver itself, as well as the antennas used and their correct placement on the vehicle