Modeling and analysis of an ionospheric mapping function considering azimuth angle: A preliminary result

Abstract

Generally, dual- and multi-frequency global navigation satellite system (GNSS) users can use dual- or multi-frequency combinations to eliminate the ionospheric delay. However, different vertical ionospheric models are applied for single-frequency GNSS users, which need an ionospheric mapping function for conversion. Although many mapping functions can be employed, the influence of latitude, azimuth, solar flux, and other factors are not taken into account. Thus, we proposed a mapping function, named SGG-MF, considering the influence of azimuth. The conversional results of single-layer model mapping function (SLM-MF), Klobuchar mapping function (Klobuchar-MF), modified single layer model mapping function (MSLM-MF) and SGG-MF are evaluated by using coinciding pierce point (CPP) technique as well as single-frequency precise point positioning (SF-PPP) in static mode. For the CPP technique, it is found that the mean absolute errors (MAE) of SLM-MF, Klobuchar-MF, and, MSLM-MF range from 1.5 to 2.1 TECU (total electron content unit), while SGG-MF ranges from 1.5 to 1.7 TECU. The standard deviation (STD) of SGG-MF improved by about 13.6%, 14.9%, and 13.6% compared with that of SLM-MF, Klobuchar-MF, and MSLM-MF, respectively. For the SF-PPP test, the positioning error of SGG-MF was reduced by about 6.0%, 22.9%, and 11.9% compared with that of SLM-MF, Klobuchar-MF, and MSLM-MF, respectively.