Smarter positioning devices through untethered dead reckoning
Exact position determination is an important precondition for many future-prone applications in and with connected cars. Normally, the solution is simple: A receiver for a global navigation satellite systems like GPS, Russia’s Glonass or China’s BeiDou does the job for little money.
But in urban canyons, tunnels or multi-storey car parks, reception of the satellite signals can suffer from reflections or even gets completely suppressed. In such situations, navigation systems typically switch over to an ancient maritime process known as dead reckoning – the system calculates its position through speed and direction of the vehicle, adding this vector up over time.
Ideally, it gets data to speed, acceleration, deceleration and directional changes from the car’s own highly exact sensors. This is how fixed navigation systems in the dashboards are working.
Aftermarket navigation systems, in contrast, typically have no access to the CAN bus and thus to the car’s sensor data, and for this reason they simply fail to determine the position within buildings, urban canyons etc – a fact that so far makes hampers the deployment of many car-related applications like insurance telematics, certain security applications or parking guidance systems within multi-storey car parks.
With its NEO-M8U, Swiss localisation and communication expert u-blox, is closing the gap. The GNSS contains a complex MEMS sensor (from Bosch) that provides all the motion data otherwise generated by the car’s sensor without the need to tap any kind of CAN bus. This enables downstream navigation system to perform something called Untethered Dead Reckoning (UDR) – computing the current position of the vehicle independently of car-based sensors.
Since the latest position is stored in a non-volatile memory, the device also provides instantaneous position data after powering up the receiver; waiting for the first GNSS fix becomes a thing of the past. The sensor data are updated 20 times per second for smooth navigation.
“This device opens new perspectives for those who develop in-car applications that need accurate positioning without the need to access the vehicle data busses”, explains Thomas Nigg, Senior Director, Product Strategy at u-blox. “Since it does not require access to the CAN bus, application creators never run into integration problems”. Potential applications could be road tolling, fleet management, security (geofencing), aftermarket navigation systems, or insurance telematics.