Introduction to RTK and dead reckoning for GNSS devices – APAC

Limitations in the accuracy and reliability of traditional GNSS create implementation challenges for IoT devices such as e-scooters and autonomous lawnmowers – making the need for mass-market availability of RTK and dead reckoning for positioning ever stronger. The inherent need for GNSS devices to ‘see’ the sky to receive satellite signals means they need assistance where obstructions arise which can block or attenuate signals, such as buildings or tunnels. Or, where poor antenna integrity interferes with the GNSS receiver, or where poor atmospheric conditions or satellite errors occur, accuracy can be lost without advanced support from RTK or dead reckoning. These allow GNSS devices to achieve much higher accuracy and consistent accessibility - through advanced modules such as our LC29H and L26-DR – by helping to mitigate common sources of degradation.

RTK (‘real-time kinematic’) positioning allows GNSS devices to achieve cm-level accuracy under poor ionospheric conditions by coordinating signals between a static GNSS base station and a mobile GNSS station ‘rover’ (i.e. the end device). Local base stations will experience the same common sources of errors and ‘know’ which corrections to make. Signals pass between the rover device and the base station through an NTRIP caster – the NTRIP caster will select the correct base station in the vicinity of the rover, then pass through the correction data. Yet while RTK is an excellent supplement to standalone GNSS, it has its own limitations, in that it cannot correct for multipath issues, or poor visibility scenarios such as tunnels. For these, dead reckoning is required.

Dead reckoning uses a 6-axis IMU with a 3-axis accelerometer and 3-axis gyroscope to estimate the position of a moving object, by referencing a known previous position, then estimating change based on speed, direction of travel and elapsed time. In untethered dead reckoning, only the IMU is used and in automotive dead reckoning, data can also be obtained from a wheel speed sensor. The gyroscope provides angular velocity which establishes orientation changes while the accelerometer provides linear acceleration to calculate distance travelled. This makes dead reckoning useful for fleet telematics, ride sharing apps and autonomous vehicle tracking.

Join our experts for this session dedicated to the fundamentals of RTK and dead reckoning, how to make the best use of their capabilities, and their implications for devices targeted at the APAC market.