Satellite-based positioning systems do not offer accurate solutions in urban environments because of propagation disturbances noising measurements. Furthermore, usual positioning computation, like extended Kalman filter, relies on considering the noise as a Gaussian centered distribution, which is unrealistic in constrained area. Moreover, today only the US system (GPS) is fully operational. Available satellite signals are not always sufficient to guarantee a continuity of service in all environments and more particularly in urban environment. However, new satellite navigation systems will appear in a couple of years. These new constellations will provide more satellites and signals. In this paper, at first, we highlight the improvement using GPS in complement with Galileo. Next, we propose a modeling of propagation noises function of the satellite state of reception, and we explain its use in the filtering process. And finally, we show some simulations results.