Global Navigation Satellite Systems (GNSS) are used in almost all fields, which can be explained by their wide availability, high accuracy, and all-weather capability. However, to achieve high accuracy, several factors affecting positioning accuracy need to be considered. The most significant factor that reduces GNSS measurement accuracy is tropospheric delay. The aim of this work is to evaluate the accuracy of determining the hydrostatic component, calculated using the Saastamoinen model, in comparison with radiosonde data; to identify seasonal variations in model errors, and to determine the causes of these variations. For this purpose, the study uses radiosonde data from five stations located at different latitudes. The hydrostatic component of zenith tropospheric delay was determined based on radiosonde data, and the same component was calculated using the Saastamoinen model. The accuracy of determining the hydrostatic component using the Saastamoinen model was evaluated, and the dependence of errors on air temperature and latitude was established.
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