Precise Point Positioning (PPP) is a stand-alone positioning technique that has continuously increased the interest of the GNSS community in the last years, as the accuracy of the precise satellite orbit and clock data products has achieved centimeter-level. Combining these products with dual-frequency GNSS receiver data, the PPP approach is able to provide solutions at centimeter to decimeter level. Apart from the dual-frequency receiver users, there is a broad range of applications that use single-frequency-only receivers. For these users, the ionosphere represents the most critical source of error. This paper carries out an initial investigation on PPP performance using single-frequency code and carrier-phase data with different approaches to mitigate the ionospheric effect, such as the broadcast ionospheric model, Global Ionospheric Maps and Wide-Area Real Time Kinematic derived ionospheric corrections. An alternative way to remove the ionosphere influence is to take advantage of the fact that the group delay in the range observable and the carrier phase advance have the same magnitude but are opposite in sign. This paper also investigates the potential of this approach. Data retrieved from IGS stations covering different latitudes and solar activity periods (high, medium, low) are considered. The results show that sub-meter-level positioning accuracy can be obtained with single-frequency-only data utilizing proper ionospheric effect mitigation methods, under optimal multipath conditions. These initial results open the way to a broader study covering other single-frequency PPP ionospheric effect mitigation strategies, as well as harsher multipath conditions.
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