GPS World, May 2017

COVERSTORY FIGURE 1 Basic workflow mode for collecting data FIGURE 2 Basic workflow mode for navigation using collected data LOOK AROUND Road Navigation Using Multiple Dissimilar Environmental Features NEW NAVIGATION PARADIGMS combining GNSS and inertial with additional sensors can increase overall reliability and power robust road navigation A feasibility study tests a barometer a magnetometer and a camera looking at road signs and concludes that such sensors examining environmental features can supply the necessary context for frequently travelled or shared routes W here a robust and reliable BY Debbie Walter Paul D Groves Bob Mason Joe Harrison Joe Woodward and Paul Wright position solution is required it is necessary to combine GNSS with other technologies Deadreckoning is only suitable for bridging short outages For robustness against longer GNSS outages alternative position fixing techniques are needed Radio based signals have been excluded from this study as they are either not yet mature or are like GNSS susceptible to jamming though they may still play a part in the final navigation solution For land navigation in particular a new approach is therefore needed Environmental features provide a potential source of location information These include buildings or parts thereof signs roads rivers terrain height sounds smells and even variations in the magnetic and gravitational fields Visual navigation technologies are being developed and are likely to be complementary to the feature matching discussed in this article however they will not be directly discussed The environmental features will be integrated with dead reckoning to provide robust positioning 22 GPS WORLD WWW GPSWORLD COM MAY 2017 The overall solution is to place hardware within a batch of vehicles comprising multiple sensors including a GNSS receiver and sensors for dead reckoning Road map matching could also be included During normal usage the GNSS receiver is used for positioning and a database is updated with the feature information from all the sensors accompanied by location stamps from the GNSS based position solution As the multiple vehicles travel around an area the database is built up for these routes In the event that the GNSS receiver does not receive sufficient signals to maintain an accurate position the database is called upon for navigation by environmental feature matching In this scenario the sensors continue to take measurements and by combining the knowledge of the last known location dead reckoning and the sensors outputs the positioning algorithm draws upon the database to estimate a positioning solution This method is shown in FIGURE 1 and FIGURE 2 This navigation system relies upon the roads being travelled on a regular basis so that the maps created from the sensors outputs are kept up to date and therefore valid The most likely users of this technology would be fleets of vehicles that can share the mapping information To focus on a typical system use in emergency vehicles was considered