GLONASS Inter-frequency Biases and Their Effects on RTK and PPP Carrier-phase Ambiguity Resolution

摘要

GLONASS uses frequency division multiplexing (FDMA) tornmake the signals from individual satellites distinguishable.rnThus, in both frequency bands the receiving equipment hasrnto deal with up to 14 different frequencies. Due to code andrncarrier-phase inter-frequency biases in the receiving equipment,rndata processing gets more difficult as compared tornGPS.rnThe carrier-phase inter-frequency biases mainly depend onrnthe receiver type and can be modeled and corrected based onrna linear function of the signal’s frequency. The code interfrequencyrnbiases are more difficult to handle since theyrnmostly seem to be receiver individual and of non-linear character.rnGLONASS Real-Time Kinematic (RTK) positioning is veryrnsimilar to GPS RTK as long as a priori corrections for therncarrier-phase inter-frequency biases are applied. PrecisernPoint Positioning (PPP), however, usually uses dualfrequencyrncode observations to resolve widelane ambiguitiesrnwith the Melbourne-Wübbena linear combination. Due to therncode inter-frequency biases this technique does not work forrnthe present GLONASS receiving equipment and it must bernsubstituted by a pure carrier-phase widelane ambiguity resolutionrntechnique.