Estimation of higher‐order ionospheric errors in GNSS positioning using a realistic 3‐D electron density model

Abstract

The accuracy of the positioning systems such as GPS, GLONASS or Galileo is heavily affected by the presence of the ionosphere. Ionosphere‐free dual‐frequency algorithms used for positioning applications remove most of the ionospheric error but do not take into account its higher‐order terms. In addition, the raypaths and total electron content (TEC) are assumed to be the same for both frequencies. This leads to centimeter‐level range errors that can cause millimeter‐level errors in positioning. In this paper an accurate estimation of the higher‐order ionospheric errors based on a realistic 3‐D electron density model is presented. A numerical homing‐in ray‐tracing algorithm is implemented to rigorously calculate satellite to receiver ray trajectories. The numerical simulations performed showed that higher‐order ionospheric residual range errors may reach several centimeters (up to 5 cm) at low and middle latitudes; however, at high latitudes they hardly exceed several millimeters (up to 1 cm).