Real-time kinematics (RTK) is a high-precision method of determining positions. This technology of the future will play an essential role in driverless applications, for example, but applications for many other industries can also benefit from real-time, centimeter-accurate measurements, including agriculture, construction, surveying, geology, robotics, and disaster control.
For such applications, conventional GNSS signals are too imprecise, with an accuracy of only three to ten meters. With the help of RTK, the accuracy can be improved to about 2 centimeters with no time delays. This ensures constant reproducibility of the position, which is essential for self-driving vehicles, not only on highways.
How does RTK achieve precise position determination?
RTK uses two GNSS receivers for positioning: a base receiver and a rover receiver. The base receiver is fixed in position and receives signals from satellites to obtain position information. These signals are referred to as correction data, as they contain information about deviations from the expected value, for example due to atmospheric conditions. For this purpose, the base receiver calculates its own location using the signals received from GNSS satellites and compares it with its known, fixed position. This allows errors and deviations to be detected and a correction signal to be generated, which is transmitted to the rover receiver in real time.
The rover is placed where the position is to be measured, e.g. in the vehicle. This means that it usually has a mobile position rather than a fixed one. Both receivers communicate with each other via a wireless connection. In this way, the rover receives the correction data from the base receiver and can increase the accuracy of the position calculation.
The two receivers communicate via a base receiver, meaning they only need an Internet connection to the receiver. The station with the strongest signal at the time of the request is always selected – even across state lines.
Does each application need its own base station?
Several satellite positioning services provide their real-time positioning data via “Networked Transport of RTCM via Internet Protocol” (NTRIP). NTRIP is a method developed by the German Federal Agency for Cartography and Geodesy to provide GNSS correction data streams. It allows access to data from existing receiver stations to ensure suppliers who integrate RTK into their applications do not need their own receivers. They can access correction data using NTRIP via public or fee-based private networks, depending on the region. A detailed list of NTRIP providers is available at ntrip-list.com.
Especially for high-volume consumer products, such as robotic lawnmowers, an Internet connection and the use of third-party NTRIP data can often be avoided. For example, the base may be a charging station, which should be immovably fixed, but whose absolute position is irrelevant. Often the mover, in this case the robotic lawnmower, communicates directly with the base via a latency-free WiFi connection. As a result, it navigates based on its relative reference to the base, rather than absolute position data.
Which components are already available?
The components needed to implement RTK applications are available from Rutronik’s GNSS portfolio. The most promising products are currently Unicore and Minew. Unicore is one of the leading companies in China in the field of positioning. The company’s customers includes some of the best-known Asian car manufacturers. In order to now also gain a foothold in the European market, Unicore is relying on a partnership with Rutronik.
In the field of high-precision positioning modules, Unicore offers various modules based on the latest generation of the NebulasIV GNSS chip and supporting different bands – also worldwide. The modules, such as the extremely compact UM960 (12.2 mm × 16.0 mm × 2.4 mm), support RTK positioning on all systems and multiple frequencies. A slightly larger module is the UM980, which also offers a higher data rate of 50 Hz (UM960: 20 Hz).
Minew’s MS34SN3 high-sensitivity GNSS module has an integrated RTK positioning engine that supports simultaneous multi-constellation positioning and L1+L5. With GPS, BeiDou, Glonass, Galileo, QZSS and RTK technology, the MS34SN3 achieves positioning accuracy in the centimeter range. At the same time, the module is very energy efficient, boasting a power consumption of only 15 mA.
What are the advantages of RTK?
RTK offers a number of advantages over conventional GPS systems. The most important are:
1. Ten times greater accuracy: This makes RTK ideal for applications that require very precise positioning, such as autonomous vehicles.
2. Real-time positioning: As a real-time positioning technology, RTK is suitable for applications that require precise and fast position data, such as drones.
3. Weather resistant: Accuracy is not affected by varying climatic conditions.
4. Versatility: RTK can be used in many industries, including surveying and geology, mining and agriculture.
For more information and a direct ordering option, please visit our e-commerce platform at www.rutronik24.com.
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