Precise GPS/GNSS positioning can be achieved only by receiving signals from three to four GPS/GNSS satellites at the same time.
When relying on GPS/GNSS only positioning, there may be cases where the position accuracy is degraded or lost. For example when the vehicle moves in areas where the GPS/GNSS signals cannot be received (tunnels or underground passages) or where very strong multipath propagation occurs (areas surrounded by tall glass covered buildings).
To overcome such limitations of GPS/GNSS positioning, a Dead Reckoning solution is useful. It enables to keep high accuracy positioning by using information from various sensors (gyro sensor, accelerometer, speed pulse, etc.) to calculate the current position, even when GPS/GNSS only positioning is difficult or impossible. Dead Reckoning solution is widely utilized in automotive navigation systems.
FURUNO's Dead Reckoning Receivers use data from Gyro sensor, Accelerometer, Speed pulse, Wheel speed data of two non-turning wheels in various combinations. A Dead Reckoning solution can easily be implemented by connecting the recommended gyro sensor and accelerometer to FURUNO GPS (GNSS) Dead Reckoning Receiver I2C terminal. Likewise, a speed pulse can be directly input to speed pulse terminal of the receiver. The sensors and speed pulse will be automatically calibrated by the receiver.
FURUNO's GPS (GNSS)/Dead Reckoning Receiver will continuously output position in tunnels using our Dead Reckoning function, but also performs hybrid positioning with GPS/GNSS + Dead Reckoning when GPS/GNSS signals are received. This function helps to achieve very high accuracy positioning even in urban canyons where typical GPS/GNSS stand alone receivers cannot perform positioning in high accuracy.
Dead Reckoning positioning
(Continuous positioning even in tunnel)
(Positioning interrupted in tunnel)
To improve the Dead Reckoning performance, FURUNO's R & D team set our own test course around the Tokyo Metropolitan Government Towers in Shinjuku, Tokyo. It is a very harsh environment of skyscrapers that reflect satellite signals and with tunnels where no satellite signal is received.
FURUNO's GNSS (GPS)/Dead Reckoning Receiver GV-87 has achieved position accuracy of 2.5m (1σ) without position shift from the road. This same environment causes loss of satellite tracking, fluctuation of ground track, position shift and position errors when observed with previous GPS stand-alone receivers.
The new GV series which detects the vehicle position in high accuracy have been developed by integrating FURUNO's conventional signal tracking and positioning calculation technologies for GPS/GNSS receivers. The GV-87 provides superior performance for the most demanding automotive applications. It has concurrent Multi-GNSS reception of GPS, GLONASS, Galileo (when operational), and highly accurate Dead Reckoning function.
The position accuracy is equivalent to or higher than that of in-car navigation system even without map matching. The GV-87 provides an excellent source of position for car navigation systems and for other automotive devices such as fleet management system, tracking devices for commercial vehicles, drive recorders, bus location systems, navigation systems for emergency vehicles where current position accuracy has not been sufficient. The FURUNO products will also help prevent accidents and contribute to safety of driving functions and vehicle-to-vehicle communication and the Advanced Driver Assistance Systems (ADAS) in the future.
Test course in Shinjuku, Tokyo, Japan
[GV-87] Position error: 2.5m (1σ)
[GPS Receiver] Position error: 10m (1σ)