Ionospheric correction using IGS Global TEC Maps: Evaluation at the GPS point positioning in the Brazilian region

Abstract

One of the main drawbacks of the GPS accuracy for L1 users is the error due to
ionosphere. This error depends on the total electron content presents in the
ionosphere, as well as of the carrier frequency. Some models have been developed
to correct GPS observables of the systematic error due to the ionosphere. The model
more known and used is the Klobuchar model, which corrected 50-60% of the
ionospheric error approximately. Alternatively, IGS (International GNSS Service)
also has developed a model called Global Ionospheric Map (GIM). These maps, in
format IONEX, are available in the site of the IGS, and one of the applications of
them is to correct the GPS observables of the error due to ionosphere. This work
aims at evaluating the quality of GPS point positioning using the IGS ionospheric
model in the Brazilian region. Tests carried out had shown an average improvement
in the horizontal and vertical determination of 72% and 26%, respectively, when
GIM is used in the point positioning.