Easy-OBU is a European Research Project co-funded in the 7th FP of the European Commission and managed by the European GNSS Agency. The main objective of Easy-OBU project is to introduce and demonstrate an inexpensive portable on-board-unit (OBU) with open interfaces that allow retrospective robust positioning of vehicles for those instances where no or insufficient signal reception from navigation satellites were available.

When the visibility to GNSS is lost (e.g. in tunnels) users of navigation systems have the choice to either wait until visibility is available again or to provide some sort of dissimilar sensor redundancy. In this regard the group of inertial sensors is the only way to provide a fully autonomous navigation unit without any interface to the vehicle. But in order to obtain accurate positioning during satellite signal outages one has to invest in expensive sensors to ensure high quality inertial navigation and is needed if real-time positioning is necessary at all times.

However if a time-delay of a few minutes once the navigation signal is available again is acceptable the project Easy-OBU examines a solution that allows retrospective calculation of the path the vehicle took with accuracy comparable to those of the original satellite signals. In addition this solution does not have to rely on expensive equipment or complicated vehicle installations.

A number of applications have already been identified and will form the basis for the definition of
user requirements:

  • Route controlling and proof of service for special vehicle fleets (e.g. for hazardous
  • goods or winter services)
  • Car sharing (pay per use)
  • Electronic toll collection
  • Calculation of CO2 Footprint
  • Public Transport: documentation of delivered performance in transport kilometre as justification for received subsidies etc.


The Easy-OBU solution relies on the use of inexpensive inertial sensors built into the on-boardunit (OBU) and an intelligent non-causal filtering (NCF) approach. The sensors capture the motion in all six degrees of freedom (translational and rotational) and are all integrated into the OBU unit and require no data exchange with in-vehicle systems. The OBU acquires the GPSfixes and the sensor data and sends this information to a central server where it is stored in a dedicated data base. This allows the application of the NCF approach in order to approximate the route taken by the vehicle during the signal outage. NCF assures that the error does not built up as it does during normal filtering operations. NCF is applied in the central server and has full access to the data base to extract the relevant position and sensor information to refine the overall quality in two ways:

  • Retrospective gap filling – improve availability
  • Compensation of large position errors – improve accuracy

An open interface from the Easy-OBU system towards the user application provides a welldefined
access to the processed and refined position data of the linked vehicle fleet. The
provided positions and trajectories can be further explored in the respective management and
control systems of the individual application.

The basic features of the Easy-OBU systems are defined as:

  • Light weight and small in size
  • Highly portable and easy install in vehicle
  • Flexible to access through well-defined interfaces
  • Highly affordable as OBU comes at low cost (including vehicle integration)
  • Flexible in regard to its usage as it may serve a whole spectrum of different applications


It is the goal of Easy-OBU to make high accuracy positioning available during navigation signal
outages at low costs and ensure integration into existing navigation applications by the use of
well documented open interfaces.

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Original Publication Date: Thu 31 Jan 2013