Introduction to RTK and Dead Reckoning for GNSS Devices

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.