GPS on‐the‐fly medium‐length positioning by an estimation of the measurement variance

Abstract This paper contributes to kinematic GPS phase ambiguity‐fixed positioning by discussing the involvement of an adaptive estimator for dual‐frequency pseudorange and carrier‐phase variances. The resulting measurement covariance matrix has a positive impact on the estimated covariance matrix of the float ambiguity parameters. Whole‐cycle ambiguities can be efficiently resolved, when transformed using a volume‐preserving diagonalization technique, especially for short baseline lengths of up to 10 km. To compensate for the lower success rate for ambiguity‐fixed positioning with long baselines (tens of kilometers), one can resort to a multi‐epoch on‐the‐fly processing technique, although the positioning accuracy obtained via this method is not as good as that obtained using a short‐baseline positioning solution. Despite double‐difference operations, ranging biases could not be completely eliminated, eventually leading to the degradation of the positioning results. The time series of the differenced ionospheric delays were then examined. In many of the observation epochs, the delays took on non‐zero values. In kinematic GPS positioning for medium‐length baselines, the estimation of residual range biases remains a challenging task, and a variance‐component estimating method can play a vital role.