Investigating the Effect of Ionosphere on GNSS Ground- Based Phase Altimetry

Ground-based GNSS altimetry by applying the phase observation is one of the new promising techniques to monitor water level fluctuations. Looking over all the factors that affect direct and reflected GNSS signals are important to improve the efficiency of this technique e.g., atmosphere effects. The troposphere and ionosphere are the most impressive layers on GNSS signal traversing through the atmosphere. This study investigates the effect of the ionosphere layer on differential GNSS altimetry observations. In spite of many studies which have considered this effect negligible, we demonstrate that this effect should be analyzed within each project. The ionosphere effect depends on electron density through the ionosphere layer (the most affecting parameter), receiver altitude, and latitude, directly and on satellite elevation angle, reversely. The numerical results through the worst case, while the electron density is maximum, receiver altitude is ۹۵۰ m and satellite elevation angle is ۱۵˚, indicate that the effect of the ionosphere on estimated water level height reaches up to ۱۴ cm and ۲۳ cm using L۱ and L۲ GPS signals, respectively.

کلیدواژه ها:

GNSS ، Reflectometry ، Ionosphere ، Phase Altimetry