The purpose of a posteriori monitoring (AM) is the estimation of different characteristics, effected upon the quality of navigation definitions by means of NSV.
The tasks of AM present the prosess fixing, when NSV operations abnormal, and also the estimation of the following parameters:
• vertical delay of navigation signals owing to ionospheric effect in L1 range;
• vertical delay of navigation signals owing to tropospheric effect in L1 range;
• errors of on-board ephemeris of GLONASS and GPS NSV;
• errors of on-board clock-and-frequency corrections of GLONASS and GPS NSV
• differences of GLONASS and GPS system time scales.
• number of observed GLONASS and GPS NSV;
• determination accuracy of horizontal and vertical coordinate components;
• determination accuracy of horizontal and vertical rate components;
Abnormal operation of NSV, is the operation, when the total effect of ephemeris errors and errors of clock-and-frequency corrections exceeds the permissible limit.