Global Navigation Satellite Systems (GNSS) receivers are special devices that are designed to receive signals from global positioning systems QZZ, COMPASS, GPS, GLONASS, as well as SBAS correction systems. These satellite devices are located in various orbits encircling our planet, or over its certain territories. Receivers (they are also satellite receivers) that have the ability to work with several systems at once are called multi-system.
These devices are used by humans to determine the exact coordinates on the ground and not only (positioning in near-Earth space is possible).In addition, they are able to measure the exact time and various parameters when moving objects (for example, direction and speed). The method by which positioning is performed is to calculate the distance between the satellite and the antenna of the GNSS receiver.
Thus, if the position of several satellites is known, then using the triangulation method it is possible to establish the position of the desired object with high accuracy, using simple geometric calculations.
The satellites themselves transmit a digital signal containing ephemeris (i.e. information about the orbit of the satellite from which the transmission is being made) and a common almanac (i.e. information about the position of all satellites in the system used), as well as updated time. The transfer of information occurs at special frequencies that are allocated for satellite transmission. As a rule, these are ranges from 1100 to 1600 megahertz.
The modern use of satellite devices has brought geodetic equipment to a whole new level - now with its help it has become easy to solve problems that are necessary not only for construction, but also for other areas of human activity. This branch of the high-precision industry is developing by leaps and bounds, various improvements are constantly appearing, so choosing the right GNSS receiver can be very difficult, due to the simple inability to keep track of new items on a permanent basis. Moreover, it is difficult to determine the receiver parameters that the user will definitely need.

Content
GNSS receivers are not only able to determine the position both on the ground and in the air, but they can also measure the properties of objects, regardless of whether they are in a static position or moving. The essence of the calculation is the continuous measurement of the distance between the satellite and the tracking object. Every year the error of such calculations steadily decreases and, accordingly, the determination of the coordinates of the tracking object becomes more accurate. At the moment, the accuracy is already several meters.
As a rule, receivers are not sold individually, but come as a set. The standard set of such equipment consists of:
Current technologies have already reached such a level of development that all of the above set can be contained in one device. The main scope of these monoblocks is cadastral and geodetic works.There are devices in which the controller is placed separately and such devices are called "handhelds". It is very easy to update the operating system and control programs in them.
IMPORTANT! It is worth distinguishing GNSS receivers from tourist GPS receivers. The first are high-precision industrial equipment and are designed for use in strictly defined areas. The latter are needed for travel and tourism and have much less functionality.
Receivers for geodetic work are divided into single- and dual-system, as well as single- and dual-frequency. Almost all modern models have the ability to take into account differential corrections for the implementation of navigation tasks. When using the latest software, it is possible to plan a geodetic survey in advance, save and transfer the received data to external devices (computer), carry out primary processing of the collected information, and form a digital map of space.
Such geodetic systems are widely used at the initial stages of the construction of buildings and structures, as well as for surveying land and linking them to geographical objects. The main advantage of using these devices is their extremely fast operation time, which allows you to transfer the received coordinates for processing almost immediately. Among other things, GNSS-coordination will allow not only to build a house correctly, but also to accurately lay various communications: from water supply to the electrical network of power lines.
As a result, the priority areas can be called:
Traditional the method is a statistical survey, which is optimally combined with all current sizes of bases. To do this, it is necessary to install two antennas in designated control points, they will process the entire amount of incoming data. The receivers, in turn, will track the satellites and record relatively similar parameters. For this method, it is possible to use the “fast statics” method - a small error is put into the script of the data received by the user, but all the necessary information can be collected within 15 minutes.
Kinematic the method is to quickly track several points at once, but in this case it is necessary to make sure that the equipment is at the desired point before the start of the initialization process (roughly speaking, until the next moment the satellite signal is received). If you do not make it in time, then the whole procedure will have to start all over again. This method is desirable to apply in relatively large areas, when it is possible to quickly reach the next point, for example, by car.
Also, the kinematic method can be used in extremely small areas, using the principle of "stop-go".In this case, the distance between the points should be minimal, and the main thing is that there are no objects in the area that can interfere with the passage of the satellite signal (high-rise buildings, power lines, etc.).
Among other things, real-time positioning is possible: the connection between the receiver and the satellite is practically uninterrupted. However, this method will require high energy costs, which the GNSS receiver battery may not be able to support. Typically, such solutions are used by cadastral engineers or topographers.
Location is critical to a successful shoot. When performing post-processing or real-time surveys with a single or dual frequency receiver, remember that the position of the rover (moving antenna) will constantly be referenced to the position of the base. Any error in determining the coordinates of the base by a moving antenna will inevitably lead to a distortion of the coordinates of the rover itself.
Thus, two conditions must be met:
There may also be a third condition, which is the environment of the base. The base antenna should be installed as high as possible so that there are no obstacles to receive the signal on the horizontal plane and the maximum range is reached.
It is necessary to make sure that the antenna is installed in a place where there are no obstacles for viewing a certain part of the sky in the vertical direction (we are not talking here about ground shielding obstacles located horizontally).Clear space above the base will allow collecting data from the maximum number of satellites flying over it. Such an arrangement guarantees the favorable operation of the system as a whole and the receipt of reliable data even from satellites in geostationary orbit, not to mention low-flying ones.

With some survey methods, it may well be that the exact position of the base is not known to the rover. Therefore, it is necessary to take the following measures: if it is necessary to achieve centimeter accuracy of measurements, then approximate coordinates in centimeters, which are known for the area where the base antenna is installed, should be used. If this is also impossible, then a small error should be included in the measurement scenario, which can then be eliminated by knowing the exact coordinates of the base.
Initialization is such a procedure, during which the receiver in real time (or the program in post-processing) can establish the ambiguity of an integer coordinate number, which is characteristic of the carrier processing phase. Such a solution is a necessary condition for the receiver and its software to obtain measurements with centimeter accuracy. Accordingly, for ultra-precise calculations, it is necessary to constantly monitor this parameter.
IMPORTANT! This process should not be confused with the initialization of the receiver by the satellite, when the primary communication is established between the devices. During the primary connection, the accuracy of the coordinates is 5-10 meters.
A key role in the operation of the receiver will be played by:
Even if the potential buyer is not a professional surveyor and has not previously dealt with such equipment, the following criteria will help you make the right choice as much as possible:
This model uses advanced ZED-Blade technology, which allows faster initialization and higher accuracy even with extended baselines. The receiver tries to make the most of all GNSS constellations, which means high efficiency and measurement accuracy even in difficult conditions.

| Name | Index |
|---|---|
| Manufacturer country | China |
| Number of channels | 45 |
| Battery life, hours | 8 |
| Operating temperature, in degrees Celsius | -20 to +60 |
| Data recording frequency | 2 Hz |
| Price, rubles | 165000 |
This sample is extremely easy to use, has a relatively small mass and a shock-resistant complex for all devices included in the set. The unique antenna design allows ultra-precise measurements in both static and real-time modes. The design of the device is an example of ergonomics, and the control interface is simple and intuitive. Most often used for landscape architecture.

| Name | Index |
|---|---|
| Manufacturer country | China |
| Number of channels | 692 |
| Battery life, hours | 11 |
| Operating temperature, in degrees Celsius | -25 to +70 |
| Data recording frequency | 1-20Hz |
| Price, rubles | 340000 |
This unit represents a new generation of receivers with a small size and advanced functionality. The receiver is equipped with automatic control of reception levels, which clearly improves the accuracy of measurements. Also, a special tilt sensor is included in the design, which allows you to eliminate centering errors and automates communications along the way. The set won the Surveyor's Best Friend 2015 Reddot Design Award.

| Name | Index |
|---|---|
| Manufacturer country | China |
| Number of channels | 220 |
| Battery life, hours | 7 |
| Operating temperature, in degrees Celsius | -45 to +65 |
| Data recording frequency | 1-50Hz |
| Price, rubles | 420000 |
This model is equipped with a special compensator that smooths out inaccuracies in measurements when the pole tilt angle occurs. Thus, constant leveling of the device is not required. It is very resistant to electromagnetic influence, which makes it possible to provide stable communication with the satellite even near power lines. The case has an increased level of dust and moisture protection (IP68). Extremely unpretentious to weather conditions.

| Name | Index |
|---|---|
| Manufacturer country | Japan |
| Number of channels | 556 |
| Battery life, hours | 7 |
| Operating temperature, in degrees Celsius | -40 to +65 |
| Data recording frequency | 1-20Hz |
| Price, rubles | 820000 |
This receiver can be called a "server from the world of GNSS equipment." It can work as a permanent fixed station, and as a reference (reference) model. The exceptional accuracy of the device allows it to be used in extremely precise areas, for example, when monitoring the deformations of the earth's surface.Has its own software "SmartWorks", focused on the performance of special tasks. Can work with many client rovers.

| Name | Index |
|---|---|
| Manufacturer country | Japan |
| Number of channels | 555 |
| Battery life, hours | 24 |
| Operating temperature, in degrees Celsius | -40 to +65 |
| Data recording frequency | 1-50Hz |
| Price, rubles | 1800000 |
Due to the fact that the described equipment is technically complex, it should be purchased only from trusted suppliers. Moreover, professionals advise making purchases on Internet sites, because there it will be possible to save on the difference in retail prices. This circumstance is most relevant, because the price of the devices is extremely high.