Patent ID: 8242954

Claim:
A method for monitoring an integrity of a satellite navigation system, comprising: determining, by system satellites, satellite locations and times at antecedent time points, on a basis of a system almanac; determining, by the system satellites and by means of extrapolation, the satellite locations and times at points at a current second on the basis of the system almanac; selecting, by the system satellites, system satellites within a visibility zone according to a target algorithm and the system almanac; receiving, by the system satellites, navigation signals from the system satellites being within the visibility zone; reading, by the system satellites, locations and times at antecedent points from the selected system satellites within the visibility zone, on the basis of the navigation signals from the selected system satellites; determining, by the system satellites and by means of extrapolation, locations and times of points of the selected system satellites being within the visibility zone at the current second on the basis of the system almanac; determining, by the system satellites, computed ranges to the selected system satellites being within the visibility zone; measuring, by the system satellites, pseudo-ranges to the selected system satellites being within the visibility zone by comparing phases of the navigation signals of the selected system satellites being within the visibility zone with own time scale; comparing, by the system satellites, the computed ranges with the measured pseudo-ranges to the selected system satellites being within the visibility zone; comparing, by the system satellites, discrepancy values with a target tolerance; radiating, by the system satellites, an uncertain navigation signal and recording an uncertainty flag to a navigation frame, if the measurement discrepancies are larger than the target tolerance; radiating, by the system satellites, a certain signal, if the measurement discrepancies are not larger than the target tolerance.