Understanding space weather dynamics is crucial when considering its impacts on different technologies on Earth. In this work, the increased Solar radiation and its influence on position degradation of two different GNSS systems are examined. At the beginning of the work, the basic theoretical concepts of satellite positioning and space weather are explained. Space weather term is described from its creation on the Sun, propagation through interplanetary space, and finally till interaction with Earth. The space weather impact is considered in two separated periods. The first period is when calm space weather conditions occurred, with no great disturbances on the Sun and Sun-Earth environment, geomagnetic field and Earth's atmosphere. After that, the period of disturbed space weather conditions is considered assuming Sun activity disturbances and its impacts on Earth, geomagnetic field and atmosphere which represent the propagation environment for GNSS signals. For interpretation of the space weather conditions, the space weather indices were used, such as Sun activity indices, geomagnetic indices, and ionosphere indices. After that, it is approached to error analysis of the U. S. GPS system and the Russian GLONASS system. Error analysis is performed using statistical analysis methods and correlation analysis on different error components such as northing, easting and vertical errors, horizontal errors and threedimensional errors. Except for error analysis, the correlation between errors and space weather indices is considered. Middle latitude station is used to retrieve position observations within a period of twelve days. The first six-day period is a calm space weather condition period, while the latter six days is the period with disturbed conditions in space weather. When error analysis is finished, the comparison between error values is represented. Comparison of results is consisted of separate comparative analysis according to each day of the examined period and group comparative analysis considering total investigation period.