Furthermore, the dead reckoning module requires calibration. The calibration depends on both sensor hardware and software configuration (even firmware changes affect the positioning quality). It is possible to manage several calibration files during runtime, according to the vehicle model and sensor configuration. When GNSS (GPS) is available, sensor data is being monitored and automatically calibrated.
However, that means there’s more data to process. Fusing inputs from various sensors into a single determinant for distance requires an understanding of network latency and other factors. Data coming from one input may not be synchronized with information from faster sensors. Controllers must have some information on latency and other parameters that impact performance. Most of the networked signals don’t have time stamps, so it’s difficult to combine them without a good understanding of many aspects of the full vehicle system.
Where do I want to go?
Most drivers don’t really care whether their navigation system is using this type of dead-reckoning information or the longitude and latitude data transmitted by GPS satellites. Instead, they’re interested in finding addresses, restaurants, stores and businesses. Navigation systems must link addresses and point-of-interest information to the desired longitude and latitude, and then figure out the best way to get there.
This is a somewhat subjective task that’s becoming more complex as technology advances. The best route can be the shortest, the fastest, or the least expensive. Picking a route is a challenging task that must be done quickly for drivers who don’t expect to wait before they step on the accelerator and start their journey.
The calculations that determine the best route must include factors like speed limits, one-way streets and turn regulations, including rules that change during rush hours. Average wait times for traffic signals and stop signs must be factored in.
Fig. 4: Calculations must include speed limits and other rules that may change during rush hours – Audi Q7 Navigation (Photo: