Improved TCAR Algorithm for BDS Over Medium-Long Baseline

Abstract

In the paper, a modified TCAR method was proposed to investigate triple-frequency ambiguity resolution (AR) performance with real BDS data. At first, the extra-wide-lane (EWL), wide-lane (WL) and narrow-lane (NL) ambiguities were determined with the classical TCAR method, and then analysis of the influence of the residual double-differencing (DD) ionospheric delay on the NL ambiguity resolution was given, and concluded that the residual ionospheric delay was the main error in the resolution of NL ambiguity over medium-long baseline. In the modified TCAR method, the estimated DD ionospheric delay was used to modify the NL ambiguity resolution. As the noise term of the DD ionospheric delay estimated from the ambiguity-fixed EWL is very large, the smooth method is employed to correct the estimated DD ionospheric delay. As a result, the NL ambiguity resolution modified by the smooth DD ionospheric delay shows a much better performance than the classical TCAR method over medium and long baseline.