Global ionospheric model with international reference ionosphere constraint

An optimized method for global ionospheric modeling with an international reference ionosphere constraint is proposed. It constrains the total electron content of the ionosphere over the equatorial anomaly area, southern hemisphere and the area where the value of the total electron content is negative. The vertical total electron content was modeled in a solar-geomagnetic reference frame using a spherical harmonics expansion up to degree and order 15. The standard deviation of unit weight derived from processing was about 1.6 TECU. The proportion of absolute residual errors was less than 3 TECU achieves above 90%. Global ionosphere maps have a good agreement with IGS, and the RMS of difference is around 3.7 TECU. The difference of the satellite's differential code bias is just about 0.1 ns when compared with CODE, and 0.2 ns compared with IGS. The difference of receivers differential code bias is about 1ns (mostly 0.5 ns) when compared with CODE, and 1.5 ns when compared with IGS. The results indicate that the global ionosphere model with international reference ionosphere constraint ensures that the values of total electron content all over the globe are positive, and enhances total electron content precision of ionosphere over the equatorial anomaly area, ocean and southern hemisphere.