Centimeter-accurate positioning in real-time.

Real-time kinematics (RTK) is a high-precision method of determining positions. This revolutionary technology will play an essential role in driverless applications and applications for other industries, including agriculture, construction, surveying, and robotics, all of which can benefit from real-time, centimeter- accurate measurements.

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.

How does RTK achieve precise position determination?

RTK utilizes two GNSS receivers: a base receiver and a rover receiver. The fixed base receiver gathers signals from satellites to obtain position information. These signals are called correction data as they include deviations due to factors like atmospheric conditions. Calculating its own location and comparing it to its known fixed position, the base receiver generates a correction signal in real time, which is transmitted to the rover receiver.

The rover, often found in a mobile position rather than a fixed one, receives the correction data and employs it to enhance the accuracy of its position calculation. Both receivers communicate wirelessly, typically relying on an internet connection to the base receiver, selecting the station with the strongest signal during the request— even across state lines.

To facilitate the exchange of correction data, many satellite positioning services provide their real-time positioning data using Networked Transport of RTCM via Internet Protocol (NTRIP). This method, developed by the German Federal Agency for Cartography and Geodesy, allows access to GNSS correction data streams from existing receiver stations. It enables suppliers to integrate RTK into their applications without needing their own receivers, accessing correction data through NTRIP via public or private networks.

For certain high-volume consumer products like robotic lawnmowers, an internet connection and third-party NTRIP data may be unnecessary. In these cases, the base could be a stationary charging station communicating directly with the mover via a latency-free Wi-Fi connection. The robotic lawnmower navigates based on its relative reference to the base rather than relying on 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, a prominent Chinese positioning company with clients including major Asian car manufacturers, relies on a partnership with Rutronik to enter the European market.

Unicore’s high-precision positioning modules are based on the latest generation of the NebulasIV GNSS chip. The modules, such as the compact UM960 (12.2mm × 16.0mm × 2.4mm), support RTK positioning on all systems and multiple frequencies. A slightly larger module, the UM980, offers a higher data rate of 50Hz (UM960: 20Hz).

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 15mA.