Patent RU-2385469-C1 (RU)
Title: Method of landing aircraft using satellite navigation system
Inventor: BABUROV VLADIMIR IVANOVICH
IPC: G01S5/02
Filed: 2008-08-25
Granted: 2010-03-27
Abstract: FIELD: physics. 
     SUBSTANCE: differential corrections of pseudoranges measured on board the aircraft with respect to satellitess are determined, taking into account the errors induced by mirror reflection of satellite signals, additionally on a local monitoring and correction station, the noise level due to radio interference of satellite signals and signals from other radio systems is monitored and transmitted to the aircraft, to evaluate the noise level of the receiver of the local monitoring and correction station (LMCS), the value of the integral signal-to-noise ratio, which is defined the average value of signal-to-noise ratios for signals of all satellites used, is introduced. On the local monitoring and correction station and on board the aircraft, time distribution diagrams of the predictable ground and on board integral signal-to-noise ratios(GIRS and BIRS) are drawn by averaging the ground and on board signal-to-noise ratios (GRS and BRS) for each satellite in conditions of normal jamming environment, the said diagrams are respectively entered into ground based and on board databases, from which the predictable values of ground and on board integral signal-to-noise ratios are continuously determined in accordance with the current time and used group of satellites, estimated values of ground and on board multipath propagation error variance for each satellite are continuously compared with a given threshold and at the local monitoring and correction station and on board the aircraft first and second groups of satellites, for which the estimated value of the ground and on board multipath propagation error variance is respectively less and greater than the given threshold, are identified, using measurements of the ground and on board signal-to-noise ratios for first groups of satellites, the current value of the ground and on board integrated signal-to-noise ratio is determined by calculating weighted average values of ground and on board signal-to-noise ratio measurements. Weight coefficients of the weighted average values are linked with the position angle of these satellites through functional relationships, ground and on board signal-to-noise ratio measurements for the second group of satellites is not used when determining the current value of ground and on board integrated signal-to-noise ratios, Simultaneously, an integrity and continuity index of the local monitoring and correction station is generated at the local monitoring and correction station and transmitted to the aircraft in a common data packet, at the local monitoring and correction station the current and predicted values of ground integrated signal-to-noise ratio are compared and if the predicted value is exceeded by the given threshold value, the integrity and continuity index of the local monitoring and correction stations is set to alarm state, and if the predicted value is not exceed by the given threshold value, the predicted value of the ground integrated signal-to-noise ratio stored in the database is corrected using its current value. On board the aircraft, data is received in a common packet and the said integrity and continuity index of the local monitoring and correction station is analysed, and if its value is in alarm state, correction of pseudoranges using differential corrections is forbidden and the corresponding warning on deterioration of accuracy of the landing system is given, the current and predicted values of the on board integrated signal-to-noise ratio are compared and if the predicted value is exceeded by a given threshold value, an alarm signal is generated, which forbids use of the satellite system for landing the aircraft, and if the predicted value is not exceeded by the given threshold value, the predicted value of the on board integrated signal-to-noise ratio stored in the database is corrected using its current value. 
     EFFECT: increased reliability of determining coordinates of an aircraft. 
     4 cl, 6 dwg