Efficiency and reliability of ambiguity resolution in network-based real-time kinematic GPS

Fast and reliable ambiguity resolution (AR) is particularly challenging in long-range real-time kinematic (RTK) global positioning system (GPS), since the atmospheric errors decorrelate with the increasing base-rover separation, effectively reducing the success rate of integer fixing. In order to improve the speed and the success rate of AR, external atmospheric corrections are required. In this paper, four different methods of ionosphere modeling are used as a source of external information, and their impact on the speed and reliability of AR and the rover positioning accuracy is discussed. An example data set, collected by the Ohio Continuously Operating Reference Stations on August 31, 2003, is analyzed, with special emphasis on varying ionospheric conditions during the course of the day in order to study the applicability of these ionospheric models to high-accuracy RTK GPS. In particular, the time-to-fix, the level of AR success, and the accuracy of the resulting rover coordinates are analyzed. Each method displays a different level of accuracy, and thus varying applicability to support AR under changing, ionospheric conditions.