Precise positioning for virtually synchronized pseudolite system

An inexpensive, flexible and precise pseudolite positioning system, developed at Fraunhofer IIS is presented. For this pseudolite system a real-time kinematic (RTK) method similar to the one employed in GNSS is applied. Because of the use of free-running clocks in the pseudolites and the characteristics of the signal, the application of RTK to the proprietary pseudolite system is challenging. A description of these challenges e.g., synchronization of transmitters and receivers, and methods to overcome them are addressed in this paper. The application of RTK allows accurate localization of a rover. The rover position is estimated through an extended Kalman filter (EKF) and the carrier phase integer ambiguity is resolved through Least-squares AMBiguity Decorrelation Adjustment (LAMBDA) method.