Sim3D is an innovative real-time system that enables the reproduction of an authentic multipath environment. The system combines a state-ofthe-art GNSS simulator and an advanced GNSS propagation model. The propagation model relies on a 3D scene of the environment, which is used to generate the multipath and obscuration signature that strictly depends on the location of the receiver’s antennawhether static or dynamic. Sim3D enables testing in fully customisable environments, ranging from deep urban to dense forest to highway. With a wide range of models available, and the ability to build and introduce your ownincluding true-to-life buildings, cars, pedestrians, and treesthe level of detail is completely in your control.