The accuracy of determining coordinates in GPS navigation and the causes of GPS errors. Determination of consumer coordinates
Measurement accuracy using GLONASS/GPS depends on the design and class of the receiver, the number and location of satellites (in real time), the state of the ionosphere and the Earth's atmosphere (heavy clouds, etc.), the presence of interference and other factors.
"Household" GPS devices, for "civilian" users, have a measurement error in the range from ±3-5m to ±50m and more (on average, the real accuracy, with minimal interference, if new models, is ±5-15 meters in plan). The maximum possible accuracy reaches +/- 2-3 meters horizontally. Height - from ±10-50m to ±100-150 meters. The altimeter will be more accurate if you calibrate the digital barometer to the nearest point with a known exact altitude (from a regular atlas, for example) on a flat terrain or to a known atmospheric pressure(if it does not change too quickly when the weather changes).
High-precision meters of “geodetic class” - more precise by two or three orders of magnitude (up to a centimeter, in plan and in height). The actual accuracy of measurements is determined by various factors, for example, distance from the nearest base (correction) station in the system service area, multiplicity (number of repeated measurements / accumulations at a point), appropriate quality control of work, level of training and practical experience of the specialist. Such high-precision equipment can only be used by specialized organizations, special services and the military.
To improve navigation accuracy It is recommended to use a multi-system Glanas / GPS receiver - in an open space (there are no buildings or overhanging trees nearby) with a fairly flat terrain, and connect an additional external antenna. For marketing purposes, such devices are credited with "double reliability and accuracy" (referring to the two simultaneous satellite systems, Glonass and Gypies), but the actual actual improvement of parameters (increasing the accuracy of determining coordinates) can amount to only up to several tens of percent. Only a noticeable reduction in the hot-warm start time and measurement duration is possible.
The quality of GPS measurements deteriorates if the satellites are located in the sky in a dense beam or on one line and “far” - near the horizon (all this is called “bad geometry”) and there is signal interference (high-rise buildings blocking, reflecting the signal, trees, steep mountains nearby ). On the day side of the Earth (lit, in at the moment, Sun) - after passing through the ionospheric plasma, radio signals are weakened and distorted an order of magnitude stronger than at night. During a geomagnetic storm, after powerful solar flares, interruptions and long interruptions in the operation of satellite navigation equipment are possible.
The actual accuracy of the GPS depends on the type of GPS receiver and the features of data collection and processing. The more channels (there must be at least 8) in the navigator, the more accurately and quickly the correct parameters are determined. When receiving “auxiliary A-GPS location server data” via the Internet (via packet data transfer, in phones and smartphones), the speed of determining coordinates and location on the map increases.
WAAS (Wide Area Augmentation System, on the American continent) and EGNOS (European Geostationary Navigation Overlay Services, in Europe) - differential subsystems, transmitting through geostationary (at an altitude of 36 thousand km in lower latitudes to 40 thousand kilometers above middle and high latitudes) satellites corrective information to GPS receivers (corrections are introduced). They can improve the quality of positioning of a rover (field, mobile receiver) if ground-based base correction stations (stationary reference signal receivers that already have a high-precision coordinate reference) are located and operating nearby. In this case, the field and base receivers must simultaneously track the satellites of the same name.
To increase measurement speed It is recommended to use a multi-channel (8-channel or more), multi-system (Glonas / Gps) receiver with an external antenna. At least three GPS and two GLONASS satellites must be visible. The more there are, the better result. Good visibility of the sky (open horizon) is also necessary.
Fast, “hot” (lasting in the first seconds) or “warm start” (half a minute or a minute, in time) receiving device- is possible if it contains a current, fresh almanac. In the case when the navigator has not been used for a long time, the receiver is forced to receive the full almanac and, when it is turned on, a cold start will be performed (if the device supports AGPS, then faster - up to a few seconds).
To determine only horizontal coordinates (latitude / longitude), signals from three satellites may be sufficient. To obtain three-dimensional (with height) coordinates, at least four coordinates are needed.
Satellite receivers are firmly entrenched in the lists of mandatory equipment for geodetic surveys and cadastral works, so it is worth understanding their purpose and features. In this article we will explain the principle of operation of GPS receivers (the GLONAS system works similarly), how they help in geodetic work, as well as differences from regular GPS modules on phones and navigators.
What is GPS?
The abbreviation GPS stands for Global Positioning System, which means “Global Positioning System”. This system was originally developed by the US Army. But over time, it “went to the people,” where many peaceful applications were found for it.
GPS consists of 24 artificial Earth satellites of the NAVSTAR family, the first of which went into orbit back in 1978. This is exactly the number of satellites needed to ensure the functionality of the navigation system. On board each of them there is a 50 W transmitter operating at a frequency of 1575.42 MHz and 1227.6 MHz, transmitting a data beam to Earth and an atomic clock, ensuring constant absolute coordination of the entire group.
The system also includes satellite receivers. There can be countless numbers of them. Both the simplest ones, installed in navigators, and the technically complex ones, found in geodetic and other high-precision equipment. The task of the receivers is to catch and record data received from satellite transmitters.
GPS measurement task
The main task that is solved in geodesy using GPS is. The system is also used in large-scale cadastral works (,) to ensure the binding of geodetic measurements relative to points of the state geodetic network (GNS).
An important issue is the choice of GGS points to which the geodetic reference network will be linked. Research has shown that it is worth giving preference to higher-class points located at a distance of 5–15 km from industrial facilities in order to eliminate the influence of man-made factors.
How GPS receivers work
Having a GPS receiver at his disposal, any user on Earth can obtain the orbital coordinates of all satellites per day, time accurate to a nanosecond, current date And exact time sending a message. Each satellite sends such information. The GPS receiver calculates the distance to it, and when receiving information from several satellites, their relative positions, as well as its own coordinates.
To simply determine the position on the ground (latitude and longitude), you will need to catch the signal from at least three satellites, and if you also need altitude above sea level, at least four. This applies to ANYONE satellite receivers. Of course, the more signals the receiver catches, the more accurately and quickly its location is determined.
The principle of determining the coordinates of the receiver is quite simple. They are obtained by resection from satellite transmitters. First things first. The transmitter and receiver have high precision clocks. In the satellite they are atomic with an error of 10¯9 seconds/year. The receivers have simpler watches, but are also much more accurate than wrist watches. The transmitter sends out an encoded signal with data about the time of transmission, its orbit and coordinates, and much more. The signal reaches the receiver at the speed of light and is processed by it. The transmission and reception times differ by an insignificant amount, but it is from these data that the distance to the satellite can be determined. Therefore, the clock must be very accurate. Distance is speed multiplied by time. By multiplying the speed of light and the travel time of the signal, the spatial notch is determined. And this happens with all satellite signals.
It turns out that at any given time the receiver simultaneously receives signals from several satellites and determines its location relative to them. It is clear that satellites are constantly moving in different orbits, and the receiver does not stand still. Taking into account these and other factors falls on the computing power of the receiver and ground-based system control centers.
The difference in GPS receivers, geodetic and conventional
First, we need to talk a little about the signals that satellites transmit. In fact, the signals are transmitted encoded on the two modulated frequencies mentioned above. Navigation receivers that do not have special decryptors (for a fee) can only process the “rough” open code sent by the transmitters. An occasional minor error was deliberately introduced into it. And it is precisely this that causes such low accuracy of conventional navigators. This was done for commercial reasons - the “unspoiled frequency” must be purchased. And the price at the moment for each frequency exceeds 100 thousand rubles. Household navigators have enough open source accuracy, so they are not as expensive as geodetic receivers.
The second difference is that the receivers in navigators work alone and determine their absolute location. That is, without additional adjustments and other receivers. They are self-sufficient. The accuracy of determination can reach 20 meters or more. And geodetic receivers work at least in pairs. One is located at a point with known coordinates (base), and the second is at a determined point (rover). They are located in relative proximity to each other (up to 50 km) and must receive signals from the same satellites. It turns out that the coordinates of the determined point are calculated not relative to flying satellites, but relative to a known point. Due to this, the accuracy of determining the position of the receiver reaches 1-2 centimeters.
Among the differences, we can note the price (multiple difference), power, internal filling, size (geodesic ones are much larger).
Methods of geodetic measurements with GPS receivers
One of the receivers must be located at the base (with a known location). The second one moves to designated points. There are several options for its movement. This is where the methodological differences lie.
The static method is the most accurate - 5mm + 1mm/km. It is necessary to observe at the point for at least 1 hour. It is used for the creation and development of geodetic support networks.
Fast-static method - accuracy is comparable to kinematic, but less reliable. Duration of observations is 15-20 minutes. Used to create condensation networks.
Kinematic method Stop-and-Go - about 1-2cm + 2mm/km. Duration at the point is about 30 seconds. Often used in topographic surveys in open areas with few contours.
Continuous kinematic method - accuracy of the order of 10-15 cm. The receiver moves continuously. Used for tracing linear objects (roads, power lines, underground communications, etc.)
With the development of GSM technologies, the most “advanced method” appeared - RTK. The accuracy is comparable to the fast-static method, but measurements take a few seconds. In Moscow and the immediate Moscow region due to the large number of continuously working base stations this method is considered preferable (if, of course, the equipment allows it).
As you can see, the methods differ in the time the receiver continuously remains at the designated point. The longer, the more accurate.
Cost of work using GPS receivers
GPS measurements are included in most engineering survey and cadastral works, therefore the cost of measurements is included in the estimate for this type works That is, these measurements are one of the stages of topographic surveying, land surveying, etc.
As a separate type, GPS determination of the coordinates of points is carried out to create reference networks for various construction and other needs. The cost of these works can be found by following the blue link on the right. The cost of GPS determinations as part of other types of work is comparable to that presented.
Don't you like that the GPS on your Android takes too long to "search for and acquire satellites"? The location accuracy is worse than 10 meters? Did you think that “this is how GPS actually works”? Nothing of the kind. Your GPS can provide an accuracy of +-5 meters, or even more accurately. And I will tell you how to achieve this. And no more “patches” or third-party and “gemorrhagic” in the use of “GPS utilities that speed up the search for satellites and increase accuracy.” Everything you need is in your device. The manufacturer simply enters “medium-light” “calibrations” there - naturally, he won’t calibrate each phone individually. And where is the manufacturer? In China, but you need to calibrate where you actually use it. The instructions below were collected by me from different sources in parts and checked, except for the part “ensuring maximum accuracy,” which I will check later and make an addition, but even without it, time “ Cold start" GPS, after rebooting the phone, it was possible to bring it to less than 20 seconds, instead of 1-2 minutes before calibration. In this case, the capture of the first satellites occurs in less than 3-4 seconds, and “GPS capture” (localization by satellites, when “stops blinking”) GPS search" and the body switches to working on satellites) - less than 10 seconds (sometimes up to 40 seconds, but less often - depending on the accuracy of your smart watch and the visibility of satellites).
To decide which one you prefer, you can read impressions of both methods here:. I personally recommend the “native GPS calibration method” (described below) - it gives the same results, and in my opinion is much preferable and easier to use.
It should be noted that with the help of the program described here: the speed of activation from the “cold” state is still a little faster. but more heroic, and because of its “deep penetration into GPS system Android", it can "throw down" the calibrations of its "native system", which are discussed below. Plus, everything that needs to be done with its help, before each turn on, the GPS makes the startup using it really slower than in the option outlined in this note.
Added 08/30/2013. Before starting calibration, look at this note and follow the procedures described in it: . This is especially true if you have serious problems with GPS, such as “it holds the satellites very poorly” and the “lock” “falls” at the slightest weakening of the signal, plus after that, the GPS will “hold” more satellites at the same time, which will improve both stability and accuracy . Without these procedures, I could not “bring the GPS back to normal” under JB 4.1.1 Cink King. Then perform calibration according to the method. outlined below in this note.
*italic font The points necessary to achieve generally theoretically possible accuracy are highlighted. Italics may be omitted, this will slightly reduce the accuracy (actually 2 times), and will not affect the “cold start” speed.
**Before the procedure, find out the code for the engineering menu of your device - you will need it.
- GPS accuracy, and especially the speed of “capture after a cold start,” greatly depend on the accuracy of the time setting on your device. Usually, in the “Date and Time” settings, “synchronize time over the network” is set. I had it too. But as it turned out, the device uses the operator’s cellular signal to set the time, which in some cases can give time setting accuracy worse than + - several minutes, and in my case (Kyiv, Life operator) it gave a difference from real time of as much as 3 seconds. In general, feces, and not “exact time signals”. There is also the option to “determine the time using GPS,” but if you don’t live in a village, then this will eat up a lot of battery, and will be of little use - neither in an apartment, nor on the subway, nor in a minibus, nor in the office... Well, you get the idea.
Therefore, let us first take care of setting the most accurate possible time. For this I set free program ClockSync, from here: https://play.google.com/store/apps/details?id=ru.org.amip.ClockSync&hl=ru, you can also get it from here: http://4pda.ru/forum/index. php?showtopic=171610 . You can also use the technique that I described here: - it does not require installation additional programs, but requires manual editing several system configuration files.
Next, we decide on the reference exact time server that we will use. It is important that it be as close to you as possible and that the ping time to it be minimal. To begin with, the addresses of the “pools” - for Ukraine this is ua.pool.ntp.org, for Russia ru.pool.ntp.org. If you are in another country, look here: http://www.pool.ntp.org/ru/.
Now we launch the terminal, and in it the command “ping ua.pool.ntp.org”, and look at the response time. We do this 10 times - each time it will contact a random “pool” server, and usually a different one. Even for Ukraine, the “response” time for different servers ranges from 5 to 60ms (on land), let alone Russia with its size. Accordingly, we write down the IP address of the server whose response time is minimal. We will use it.
Let's launch installed program ClockSync, Menu > settings. The first item is "NTP server". Enter the selected IP address there. Next, check the box " automatic synchronization", then select "Interval". The smaller the interval, the more often the synchronization will take place, and this is "a little traffic and a lot of battery", on the other hand, in 3 hours my device “goes away” by as much as 160-180 milliseconds... I settled on 3 hours for now. Next, you don’t have to check the “exact interval” checkbox - it will save the battery a little, I personally checked it. "High precision mode" - check it, especially since synchronization will sometimes go through cellular transmission data at a very unstable speed (you don’t have to set it - the accuracy will drop, but the battery consumption during synchronization will significantly decrease). We also set “define time zone”,
Exit the settings menu, click “menu”, and select “synchronize” - how much your device is “past time” can be seen on the screen. Yes, in the settings menu after a day you can see how fast/late your device’s clock is per day (my Fly IQ 450 is 9.21 seconds per day).
PS automatic time synchronization is only possible on a “rooted” device. If you are not rooted, there is in the program " manual mode", but the accuracy will not be the same.
Note - added later. There is also a second way to accurately synchronize time, without installing an additional program, I described it here:. After comparing the results, I chose this method, but it requires some editing of the configuration files.
It is also advisable, if you have a rooted device, to edit the /system/etc/gps.conf file. Namely, in the first line, after “NTP_SERVER=", replace the “default” one indicated there with a more suitable one for your country - for example, for Ukraine at ua.pool.ntp.org, or even with a previously defined IP address, but this will less universal and sometimes fraught with failures if a specific server does not work, so ua.pool.ntp.org is more universal, but the IP address in this field can further speed up the initial cold start. Editing can be done using "Root Explorer".
Over time we figured it out. Next. - Let's go to the phone settings. Location. We mark the points: “By network coordinates”, “ GPS satellites", "Auxiliary data", "AGPS", the rest is "to taste". Now go to the "EPO Parameters" item. Turn off "EPO" for the duration of calibration. That's all.
- Launching Google Earth , In the settings, we switch it to show coordinates in the format of degrees and fractions. We are looking for a place nearby where we will carry out calibration. It should be a fairly open place, such as a square. We select the point where we will stand during calibration (select signs to stand exactly at it later), point the cursor at it, and write down the shown coordinates to the last digit. The preparation is over - let's go "to the field" :) with the phone.
- If you used p3- we stand EXACTLY at the point we previously selected. Let's launch " root explorer", go to the /data/misc folder, delete the mtkgps.dat file. We download the latest AGPS data - for example, through the GPS Status program (menu>tools>AGPS Data>Load). We check the time, for example with the ClockSync program (we check it several times, look typical deviation, and then click synchronize - how to use the program and where to get it - see earlier in the article on time calibration). Go to the engineering menu, LocationBasedServices, select “GPS” in the menu, and press the “GPS” button (the inscription on it will change from OFF to ON). Go to "View". We wait until the “fix” appears (the GPS indicator stops blinking), and then for at least another 2 minutes. Then click RefPosition, and in the windows that appear, enter the coordinates previously recorded from Google Earth for the point where you are calibrating (there will be zeros there). Click "OK". Go again to View screen, and wait after the “fix” for at least 2 minutes, preferably 5 minutes. We go back to the engineering menu. If step 3 was not performed, simply choose any fairly open place. Taking out- don’t even try to do the calibration on the balcony or “from the window” - you’ll only make it worse.
- ****You can also check the correctness of your choice before calibration SIM cards for AGPS - if your mobile operator“glitchy”, and there are two cards and two operators, then you can choose a less buggy one, this if “buggy” was selected, can significantly speed up GPS operation, and then “revive” the “completely broken GPS” procedure is described at the very end of the note.
- Go to the "Engineering Menu"(for my FLY IQ 450 and many Chinese clones, this is the code *#*#3646633#*#*, which we dial where you usually dial the phone number when calling, you may have a different one). Find "YGPS location" and launch it. Hold your phone vertically.
- Go to the Information tab. Click the "Full" button.
- Go to the "Satellites" tab, wait until at least 5 satellites appear (preferably more - I had 11 of them when setting up), and after they “appear and turn green”, wait at least another 2 minutes, holding the device motionless (it can be longer - it won’t be worse - only better ). This is the initial calibration. It took me about 3 minutes, but for some devices, according to reviews, it can take up to half an hour.
- Go to Information", click "Cold". Continue as in point 8. Repeat point 9 3 times. More is possible.
- Back to Information. Click "Warm". further as in paragraph 8. There is no need to repeat it anymore.
- Back to Information". Click "Hot". Continue as in step 8.
- If you followed step 3, go to the engineering menu, select the "LocationBasedService" item, go to the "View" tab (remember to activate GPS as described in step 4), and wait until the maximum satellites are determined. Minimum 7, better more (the more, the more accurate the calibration), and after the maximum is determined, wait another 2 minutes. Then go to the tab GPS, and click "RefPosition". You will have two numbers, from the one you previously recorded using Google Earth, they will most likely differ in thousandths. Correct both to those that you wrote down earlier in step 3. Click "OK". Now go to the GPS tab and wait for 5 minutes holding the phone motionless. Here in this place - the longer the better. GPS program, having received real coordinates, compares them with those that she “obtains” and makes corrections. clarifying them. Below in the window you will see a “process” counter and data that changes from time to time.
- Exit the engineering menu and reboot the phone.
- All. We rejoice in the fast and accurate GPS.
PS If you are also going to use the program described here: then please note that you need to calibrate after installing it. And if it is uninstalled, calibrate it again - it resets the calibration data during uninstallation, and the GPS again begins to “search for satellites for several minutes.” Loading its “acceleration” data does not SEEM to affect the calibration, but it also makes no sense - the difference in speed is “within the limits of statistical error.” But it seems that the real accuracy is a little better, with freshly downloaded data (by 20 percent, but also within the statistical error in essence). Also keep in mind that the downloaded data from the above program quickly becomes outdated, and after a day or two, on the contrary, it will slow down the GPS and reduce accuracy (compared to a simply normally calibrated native one using the method described above in this article). Plus, I took it down nafik :) Bo, firstly, is not needed, and secondly, with it you can get “GPS which does not determine anything” if you forgot to download new data. Even if you clicked the “reset downloaded data” button and do not launch the program itself. At least this happened to me once - I didn’t check the rake again.
PPS There are rumors on the net that “turning on EPO data” (specific GPS data for MTK chips), which gives some acceleration of the “cold start”, reduces the number of “captured satellites”. This is unlikely. The number of captured satellites is determined by their “number overhead at the moment” and their height above the horizon (in the city, those above the horizon are usually not visible). But still, when calibrating it is better to turn it off. And use only if you are traveling to a place where the Internet may not be available. Then it will give you a real launch acceleration (it downloads data a month in advance). IN normal situation It’s better to use only AGPS - its data is fresher, and therefore more accurate, so the “start” speed with it is typically higher.
PPPS Below is “reference information” for those who received a device with a completely non-working GPS. It’s worth checking it - the reason may be that you have something different from the following listed in your settings:
IN engineering menu, in the LocationbasedService item, in the AGP tab S:
Enable A-GPS, MSB, User Profile, SLP Template - GOOGLE, supl.google.com, 7275, TLS Enable, RRLP, IMSI, K-Value must be enabled.
Horizontal Accuracy - 22, Vertical Accuracy - 0, Location Age - 0, Delay - 0. Location Estimate is selected.
*********Selecting a SIM card for AGPS
Go to the NET tab - select - click look at the map (Map tab), the address where you are located, or close to it, should appear there. We do the same with . We compare what is more accurate to yours real situation, and on the AGPS tab select your preferred SIM card.
On the AGPS tab, click
Yes, if any of the things listed in this PS differed from the settings of your device, or if you changed the SIM card to which you have AGPS attached, you need to perform a new calibration.
PS About the influence of clock accuracy on the GPS cold start time.
From the “inconvenient place” - a balcony, everything on top is covered with concrete, a courtyard-well - houses on 4 sides, the sky is a “piece from above”, 4 satellites are barely visible (then you can barely see 3, and the 4th one appears and disappears). The phone was calibrated according to the method outlined above (before calibration, there was no capture at all under these conditions). The clock “lags” by ~160ms (2 hours have passed since the clock was calibrated by the ClockSync program). Cold start time ~250-300 sec. After forced time calibration by the ClockSync program, the “cold start” time is ~100 seconds. However, these are the conditions. in which GPS usually does not work at all, but clearly illustrates the effect of clock accuracy on the “cold start” time.
PPS To force the loading of AGPS data, for example, if you are far from the place where they were downloaded - for example, you went 200 kilometers for fishing/vacation, etc., and the AGPS data downloaded at home has become irrelevant, which can negatively affect the “cold start” time.
You can use the GPS Status program from here: https://play.google.com/store/apps/details?id=com.eclipsim.gpsstatus2&hl=ru. Launch this program. At the bottom left under the “coordinate circle” is the age of the AGPS data in hours. Click Menu > Tools > A-GPS Data. Then "download".
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 Federal Law dated July 24, 2007 No. 221-FZ “On the state real estate cadastre” (Collection of legislation 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 boundary 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 UCS 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 assumed 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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Copyright Infringement and Personal Data Violation
Testing the accuracy of GPS receivers on 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 Motorola smartphone 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 little disappointed - for its price the results were expected to be better.
But most of all I was surprised 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- the only one who always and everywhere on an airplane from a cold start finds satellites and calculates coordinates. Despite the apparent good conditions reception, 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.
Remember how many times you swore at an innocent navigator, finding yourself on the wrong exit, on the highway instead of an understudy, on an unfamiliar sofa with your face covered in toothpaste... Well, okay, in the latter case, the navigator has nothing to do with it. But if you think about it, the device is not always to blame for other wrong turns.
Birmingham, England
The software in a navigator or smartphone works with GPS chips, in which nothing has changed for years. And in satellites that have been circling in orbit for decades, nothing can be changed at all. And yet the American corporation Broadcom intends to change the existing order of things.
An interchange passing through a high-rise building. Osaka, Japan
At the ION GNSS+ conference in Portland, a prototype of a commercially mass-producible BCM47755 GPS chip with an accuracy limit of 30 cm instead of the current 5 m was presented!
Shanghai, China
Among other things, the chip consumes half as much energy (smartphone owners open champagne!) and does not get confused in the palisade of high-rise buildings. Broadcom representatives claim that some smartphone models that will go on sale in 2018 will be equipped with the new chip. But here’s the annoyance: they don’t say which ones.
Swindon, UK
Any satellite navigation receiver, be it the American GPS, Russian GLONASS, European Galileo or Japanese QZSS, works approximately the same: it calculates its location from a signal about the exact location of three or more satellites, using different data, for example, the time it takes for the signal to travel between the satellite and the receiver.
Springfield, Virginia, USA
Why are new GPS chips being launched now? Firstly, Broadcom has mastered the production of processors on 28-nanometer architecture. And secondly, the constellation of new generation navigation satellites has increased. There is more than one format for transmitting data by satellites. Standard precision L1 signals have been in use for quite some time, but now the more powerful and broadband L5 signal has come to their aid. According to Broadcom, even with limited sky visibility in large cities, GPS devices simultaneously “see” six to seven satellites, and this is quite enough for the new high-precision chips to work.