GPS and GLONASS Integration: Modelling and Ambiguity Resolution Issues

The integration of GPS with GLONASS may be considered a major milestone in satellitebased positioning, because it can dramatically improve the reliability and productivity of said positioning. However, unlike GPS, GLONASS satellites transmit signals at different frequencies, which results in significant complexity in terms of modelling and ambiguity resolution for integrated GPS and GLONASS positioning systems. In this paper, a variety of mathematical and stochastic modelling methodologies and ambiguity resolution strategies are analysed, and some remaining research challenges are identified. The exercise, of developing mathematical models and processing methodologies for integrated systems based on more than one satellite system, is a valuable one as it identifies crucial issues concerned with the combination of ANY two or more microwave positioning systems, be they satellite-based or terrestrial. Hence these are experiences that can be applied to future projects that might integrate GPS with Galileo, or GLONASS and Galileo, or all three.