A Map Based Virtual Satellite for Weighted Least Square Enhancement

Reliable GNSS based positioning for vehicles in urban environments is a challenge. Availability of single satellites, satellite constellations or receiver and multipath errors are compounding this task. This work presents a method to define an additional virtual satellite for GNSS position determination. This additional measurement is generated from a lane level map with an included digital terrain model. The virtual satellite has its position in the origin of the earth centered earth fixed (ECEF) coordinate frame. With the map associated 3D position a virtual range can be calculated. This virtual range combined with GPS ranges is used in a weighted least square method. To have a useful weighting matrix the variance of the virtual measurement has to be considered. This work also contains the integration of the enhanced position calculation into an existing localization fusion. A conducted test drive in different environments will show the performance of the developed concept.