HIGH ACCURATE POSITIONING FOR AUTONOMOUS VEHICLES ENABLED BY CONNECTIVITY

The deployment of autonomous vehicles in our roads within the next future requires high accurate positioning information. It allows for vehicles to navigate in the correct lanes, position themselves correctly so to be able to affect future manoeuvres. For this purpose, several solutions have been developed to estimate the absolute and relative position of these in real-time. The only source available to estimate their absolute position is through the use of Global Navigation Satellite Systems (GNSS). To place vehicle positioning within the stringent requirements that autonomous driving demands, much effort has been made in recent years to bring to the automotive sector the advanced error correction techniques applied in other domains like aviation. These include error correction in the position computed by a GNSS receiver using PPP algorithms (Precise Point Positioning). As PPP signals can be broadcasted widely, costs can be shared and thus be low, hence the attractiveness for the automotive industry. To operate, PPP uses a feature available in most modern vehicles - that is connectivity. Cellular communications allow the downloading of correction data that is computed with the positioning information processed by a GNSS receiver. The algorithms using the PPP signals output location estimates with an accuracy of a few centimetres, which respond to the needs of autonomous driving. This paper presents state-of-the-art in positioning technologies valid for the autonomous driving requirements. It focuses on a solution to exploit the possibilities of GNSS systems based on on-board connectivity. The manner how this solution is implemented and verified in public roads as part of the ESCAPE project is detailed. The ESCAPE project, funded by the European GNSS Agency, researched around the referred technologies with the aim to develop a precise positioning system for autonomous vehicles. ESCAPE applies PPP corrections to the GNSS data processed by an advanced dual frequency multiple constellation GNSS receiver. PPP corrections are downloaded from the Internet through the cellular link that the unit provides. They are combined with vehicle odometer data and other on-board sources. The system outputs high accurate positioning, velocity and time (PVT) information together with integrity information in the form of protection levels. The latter is needed to satisfy the safety requirements of autonomous vehicles. The developed system was designed to respond to the positioning needs of autonomous vehicles, nevertheless its capabilities can be used too in different types of driving assistance systems. The advanced positioning features in the ESCAPE system can be an invaluable aid to maximize the use of regulation services such as the emergency call. The availability of precise position is an enabler for applications requiring spatial-temporal information like in the case of vehicle to vehicle and vehicle to infrastructure communication technologies. Further the coming 5G networks shall enable other applications.