Processins GLONASS Carrier Phase Observations - Theory and First Experience

Abstract

The GLONASS (ICD-92) double difference carrier observables must be transformed to either a common frequency or to linear distances in order for the relative receiver clock errors to cancel. Such a scaling causes the double difference equations to contain single difference ambiguities whose coefficients depend on the GLONASS frequencies. Pseudoranges are used to compute an approximate single difference ambiguity value for the base satellite. This additional step, which is not required for GPS, allows the double difference ambiguity formulation. However, this initial approximation of the single difference ambiguity must meet certain accuracy limitations. Dual- frequency pseudoranges and carrier phase observations to 5 GLONASS satellites are used to verify software implementation and to draw conclusions such as the need for frequency-dependent hardware delay calibrations and the need for accurate pseudoranges.