Influence of the Atmospheric Water-Vapor Field Irregularity on the Phase Measurements of Radio Signals from Global Navigation Satellite Systems
In this paper, we present the experimental-study results for the horizontal gradients of the integral content of atmospheric water vapor, which were obtained from the phase measurements of signals in the receiver network of the global navigation satellite systems in 2011 in the Republic of Tatarstan. The seasonal gradient variation is found. The meridional gradient usually shows a moisture-content decrease with increasing latitude and its monthly averages are equal to -1.8 mm and 0.1 mm of precipitated water per 100 km in August and December, respectively. The zonal monthly average gradient is somewhat smaller than the meridional one by absolute value and equals 0.1 mm and -0.8 mm per 100 km in March/June and May/October, respectively. Instantaneous values of the gradients can by an order of magnitude exceed the monthly average values. Contribution from the integral moisture-content gradient to the phase-measurement difference between two antennas spaced at 30 km is shown to attain its maximum 141.5 mm in August for the zenith angles 80°. Errors in determining the mutual location of the ground-based antennas of the global navigation satellite systems due to moisture content can reach 66 mm and 16.9 mm in August and February, respectively.