Uzhgorod State University, Uzhgorod, UKRAINE
The atmospheric refraction causes changes in the velocity retar- dation and in the direction of electromagnetic waves (bending) along the propagation path and introduces a delay in the time of arrival of transatmospheric signals. The most significant effect is the de- lay which can be divided in to an ionospheric and tropospheric one, which is considered in this paper. Radiosonde data are used to exa- nine the accuracy of several models for tropospheric delay predicti- on on the base of surface meteorological measurements.