Estimating the absolute total electron content from the single-frequency GPS/GLONASS data

We present a technique to estimate the absolute vertical and slant total electron content (TEC) of the ionosphere. Estimating is based on single-frequency GPS/GLONASS data of joint phase and pseudorange measurements from individual station. The absolute vertical TEC estimation is performed based on second-order space-and-time Taylor expansion of TEC. We have compared the absolute vertical TECs obtained by single-frequency and dual-frequency data as well as global ionosphere map (GIM) data. Our analysis shown that quality of the single-frequency measurements of the vertical TEC differs not so much from the same estimates based on the dual-frequency data.