<1> The global numerical model of the thermosphere, ionosphere, and protonosphere of the Earth, making it possible to calculate all the main parameters of the near-Earth plasma, is used to calculate the total electron content (TEC). The calculations are performed along the ray of the signal propagation between the ground-based reception point and a GPS system satellite. The values of TEC calculated according to satellite data are compared with the "true model" value of TEC for magnetically quiet conditions of the spring equinox at moderate solar activity. Relative errors in determination of the satellite TEC for two European stations Brest (48.5o N, 5.5o W) and Kaliningrad (55o N, 20o E) are calculated. It is demonstrated that an increase of the number of the observed satellites does not always lead to an increase of the accuracy of the TEC measured with the help of the satellites.