The paper presents the results of an experimental campaign of the GNSS transmitter-based approach for indoor positioning. Details on the chosen setup are given and the main features of the system are described in full. Comments on the positioning accuracies obtained, together with the description of the real environment are provided and an analysis of the performance of the system is proposed. For the next few years the continuity of the positioning service indoors will continue to be a real challenge. GNSS, sensor networks or WLAN approaches have been proposed in order to provide this continuity [1-4]. The GNSS-based approaches aim at making a better exploitation of the satellite signal on the receiver side. Unfortunately, techniques like HS-GPS or A-GPS [5-6] do not seem to provide a definitive solution. Local infrastructure-based solutions can help establish a final system with good accuracy and a wide coverage: the approach described in the paper uses GPS transmitters that make GPS signals available indoors