Building a regional tomographic model for the inospheric changes over Korea based on GPS measurements

We present a GPS-based regional ionosphere tomography model, which estimates Total Electron Content (TEC) in several layers over Korea. The GPS data from all available Korea GPS stations were used. The two-dimensional ionosphere model was grid-based, and the three-dimensional ionosphere model used a tomography technique. The pseudorange data were phase-leveled by a linear combination of pseudoranges and carrier phases. The solar-geomagnetic coordinate system, which is less variable to the ionosphere movement due to the Sun and geomagnetic field than an Earthfixed frame, was used. During a quiet day of solar activity, the regional ionosphere map indicated 30-45 Total Electron Content Unit (TECU) at the peak of the diurnal variation. In comparison with the Global Ionosphere Map of the Center for Orbit Determination (CODE) in Europe, RMS differences of twodimensional grid-based model were at the level of 3-5 TECU. Keywords-component; GPS, ionosphere, tomography, TEC