Patent ID: 8310395

Claim:
A method of amending navigation data of a global navigation system comprising a plurality of space vehicles that transmit information to at least one device for position detection; wherein: each space vehicle has at least one clock; and the impact of space vehicle navigation data anomalies, including clock frequency jumps, on the at least one device for position detection is reduced by a ground mission segment performing the steps of 1a) receiving navigation signals from a space vehicle; 1b) estimating a prediction of a clock phase offset of a clock signal sent from the space vehicle, and storing this prediction in a memory; 1c) computing at a current measurement and monitoring epoch (t 0 ) a clock phase offset difference (d 0 ) between the estimated prediction of the clock phase offset obtained in step 1b) and a previous estimation for said clock phase offset of a first earlier epoch (t −1 ) within a given time interval (T 1 ) and storing the clock phase offset difference (d 0 ) in a memory; 1d) obtaining an earlier computed phase offset difference (d −1 ) from the memory wherein said earlier computed phase offset difference (d −1 ) was computed and stored at a second earlier epoch (t −2 ) according to step 1c) between a previous estimation for said clock phase offset of said second earlier epoch (t −2 ) and a further previous estimation for said clock phase offset of a third earlier epoch (t −3 ) within the given time interval (T 1 ), wherein a time interval (T 2 ) between the current measurement and monitoring epoch (t 0 ) and said second earlier epoch (t −2 ) is equal to or greater than T 1 ; 1e) deriving a difference (Δ 0 ) between the clock phase offset difference (d 0 ) computed in step 1c) and the earlier computed phase offset difference (d −1 ); 1f) comparing the difference (Δ 0 ) derived in step 1e) with a threshold value; 1g) generating an integrity risk signal if the difference (Δ 0 ) derived in step 1e) is greater than the given threshold value; and 1h) transmitting the integrity risk signal to the at least one device for position detection of the global navigation system.