Improving the Single Point Positioning Accuracy in a Multi-Frequency Context with the Estimation of the Ionosphere Delay

Classical methods for satellite navigation build ionosphere-free combination in order to remove the delays caused by the propagation of the signal in the atmosphere, and in particular the ionosphere. Since this signal combination has been set up in the early ages of the satellites navigation systems, it only uses two frequencies. This article proposes to explore ionosphere-free combinations with all the available frequencies. Such combinations always increase the observable noise. Therefore, an exploration of a Kalman filter estimating jointly the geometric and ionospheric parts of the observable models is performed. The results are applied in cases for low and high solar activities. As the new solar cycle begins, the ionospheric effects will be of importance for the years to come.