Abstract:Nowadays ground-based global navigation satellite system (GNSS) stations of the international GNSS service (IGS) are distributed unevenly around the world,especially in the southern ocean area. As a result, many unreasonable negative vertical total electron content (VTEC) values appeared in corresponding areas referred above. To completely eliminate non-physical negative values, a new method, temporarily named SGG, with IGS’s final VTEC products is proposed for constraining the area where no real data is available, and then we process the GNSS dual data of more than 200 IGS reference station in 2014(high solar activity year) with GIM constraint to validate the new method. The results have shown that the RMS of ionospheric TEC at contributed stations is within 3 TECu in the spatial domain(the RMS over the equatorial anomaly area is approximately 5-7 TECu). Meanwhile SGG efficiently eliminates the unwanted behavior of negative VTEC values in ocean and middle-high latitude areas of the southern hemisphere(40°-90°S), and the original positive VTEC almost won’t be affected(the variation of VTEC can be controlled within 2 TECu).The satellite and receiver DCB of SGG is also highly consistent with IAACs, the RMS and MEAN of satellite DCB between SGG, UPC, ESA, JPL and CODE is within 0.2 ns and 0.04 ns respectively. The receiver DCB valuation changes between SGG and CODE at different latitudes are basically identical(the difference is about 0-1 ns).