On the accuracy of the gradient method for determining the mean integral refractive index of air for large-scale dimensional measurements

Abstract

The results of the analysis of the accuracy capabilities of the gradient method for determining the mean integral value of the group refractive index of air along the path of the laser radiation propagating on the surface atmospheric layer are presented. The mean integral refractive index of air is used in precision laser ranging as a correction to the results of large-scale dimensional measurements, taking into account the difference between the speed of the laser radiation propagation in the atmosphere and the speed of light in vacuum. The performed analysis includes a critical review of publications underpinning this method, and the prospects for its use in high-precision laser measurements of horizontal baselines of up to 5 km long with an expanded uncertainty of less than or equal to 1 mm are considered. This method has been studied in the framework of the Project 18 SIB01 GeoMetre “Large-Scale Dimensional Measurements for Geodesy” executed in accordance with the European Metrology Programme for Innovation and Research (EMPIR).