The article presents a field testing of an algorithm for refraction coefficient determining from gradient geodetic measurements for unilateral trigonometric levelling. The algorithm developed by the authors is based on solving by the Monte Carlo method a system of nonlinear equations describing the vertical refraction angle changing in the working air layer. The authors performed analysis of the factors of vertical refraction formation, which to be taken into account in the production of gradient (at several levels) geodetic measurements. It is noted that the successful implementation of the developed algorithm is possible under the condition of unidirectional changes in the vertical atmosphere profile, i. e. in the absence of layers with different atmospheric stratification character. At the stage of preparing field observations, first of all methodological approaches for the production of gradient geodetic measurements were developed. These approaches are based on the analysis of the factors of vertical refraction formation which to be taken into account. Besides a procedure for angular measurements at several levels was proposed. The proposed procedure ensures the efficiency and accuracy, which are necessary to obtain the initial data for the refraction coefficient determining. The performed field observations and the further analysis of the obtained results proved the possibility of using the trend of changes in the increment of the refraction angle with height as an objective criterion for detecting atmospheric stratification change in the working air layer. The accuracy evaluation of the elevation differences corrected for the refraction influence using the algorithm developed by the authors showed that the results obtained met the requirements of geometric levelling of class IV.
Valov et al. (Fri,) studied this question.