The Measurement of the Ionospheric Total Electron Content Using P-Code of GPS

It is generally known that the measurement of the ionospheric total electron content(TEC) by GPS can more accurately monitor the broader area of the ionosphere than other current methods. We measured the TEC along a slant path considering the arrival time differences of P-code which is transmitted from GPS satellites with the modulation on two L-band carrier frequencies, L1(1574.42MHz) and L2(1227.60MHz). Under the assumptions that the ionosphere is uniformly distributed and its average height is 350km, we transformed the slant TEC to the vertical TEC at the point that the line-of-sight direction to GPS satellite cut across the average height of the ionosphere. Because there is no dual frequency P-code GPS receiver in Korea, we used the data observed at the TAIW GPS station (N25¢ª, E121.¢ª5) in Taiwan which is one of the core stations in International GPS and Geodynamics Service (IGS). The TEC values obtained in this work showed a typical daily variation of the ionosphere which is high in the daytime and low in the nighttime. Our results are found to be consistent with the SOLAR-DAILY data of NOAA and the Klobuchar's model for the ionospheric correction of GPS. In addition, in the comparision with SOLAR-DAILY data, we estimated the precision of our TEC measurement as 2 TEC