System and method for establishing the instantaneous speed of an object

System for establishing the instantaneous speed, in a reliable manner, of an object (1) which is travelling along a known trajectory, in particular a vehicle such as a train, the system comprising:

• means (3, 7) for approximately locating the object and direction of its movement, and
• means (6) for receiving at least one signal transmitted at a predetermined frequency, known to the object, from at least one satellite (4, 5) and
• means (8) for calculating and analysing the signal comprising:
• means (10) for measuring the frequency shift of the signal received relative to the predetermined frequency of the signal transmitted, which means (10) are connected to
• means (12) for establishing the vectorial difference of the speeds of the object and the satellite in the satellite/object direction by calculating the Doppler effect which has generated the frequency shift and
• means (13) for calculating the instantaneous speed in the movement direction of the object based on the vectorial difference established previously, characterized in that the measurements of the frequency shift and the associated calculations are repeated independently on signals from at least two different satellites, and in that the calculation and analysis means (8) further comprise means (14) for combining the results obtained independently in order to obtain an instantaneous speed with the desired level of reliability.