A method and system for estimating an angular deviation from a reference guidance axis, a position and a velocity of an aircraft. The system includes an offset collection module for collecting an offset measured by a measurement module, a position vector collection module for collecting a position vector measured by a position vector measurement module, a velocity vector collection module, a module for estimating the angular deviation of a reference guidance axis with respect to the approach axis towards the runway, for estimating the position of the aircraft with respect to the runway and for estimating the velocity of the aircraft with respect to the runway.