For the average driver, pin-point precise location and navigation are handy tools that save time and mileage. But for the emergency services, fleet management and stolen vehicle recovery, reliable, uninterrupted, three-dimensional positioning that doesn’t rely on regular map software updates can be the difference between success and failure, and sometimes life or death.
However, the problem with a typical “Automotive Dead Reckoning” (ADR) vehicle navigation system is that they rely on a filtered position from a standard GNSS receiver and fuse it with filtered external sensor data from gyro, accelerometer and/or wheel tick sensors.
The filters used for both the GNSS receiver and sensor data are Kalman, or linear quadratic estimation (LQE) types that implement an algorithm that uses time-series measurements to estimate unknown variables. The real-time filter first estimates the current state variables with their uncertainties, then uses the next measurement to update these estimates using a weighted average calculation. However, cascading two Kalman Filters introduces an accumulation of errors that can degrade positional accuracy, which is why navigation systems are becoming increasingly dependent on map matching algorithms to compensate.
So the question is whether map matching – the process of positioning each point of a mobility trajectory on a digital map – is really the answer to what is essentially a filtering problem? On the contrary, it creates a dependency on 3rd-party providers of map data, whilst requiring software and resource development overhead to interface the GNSS receiver to an external mapping service.
A more successful approach is being taken by u-blox, which has developed an ADR algorithm that blends data into a single Kalman Filter. The solution combines satellite navigation data with individual wheel speed, gyroscope and accelerometer inputs to accurately track position in urban environments without relying on external map data.
There are two components to u-blox’ 3D ADR solution: the UBX-M8030, which integrates the core ADR technology into a chip; and the NEO-M8L, a compact, GNSS satellite positioning module. The self-calibrating ADR chip supports various sensor combinations including wheel ticks, single-axis/3-axis gyroscopes and single-axis/3-axis accelerometers. A plus point of the ADR chip is that it receives sensor data from the vehicle’s CAN bus via the host processor, cleverly reducing hardware costs since no extra sensors are required for dead reckoning functionality.
The NEO-M8L is the first of its kind to integrate a 3D accelerometer and gyroscope with a global positioning chip. With a navigation sensitivity of -167 dBm, it provides a precise geo’ location for a vehicle even in tunnels, parking garages and multi-level roads. The module boasts u-blox’ M8 concurrent positioning engine which receives and tracks multiple GNSS systems (e.g. GPS, GLONASS, Galileo-ready, BeiDou and QZSS signals). By default M8 receivers are configured for concurrent GPS and GLONASS reception and if power consumption is a problem, the receiver can be configured for single GNSS operation using either GPS,GLONASS or BeiDou.
A reduced reliance on map matching and improved GNSS accuracy means that the next generation of in-built ADR systems promise more than ever to make wrong turns a historical motoring footnote in our increasingly interconnected world.