The use of zenith distances to determine the individual angles of refraction
We give the basic equations for determining the individual angles of vertical refractions by the methods of refractive relationships.
zenith measuring
Effective ways of taking into account refraction when measuring zenith distances
Improving the results of trigonometric leveling and taking into account the influence of refraction in the measurement of zenith distances became possible due to the appearance of modern accurate and high-accuracy theodolites, which allow to minimize the influence of instrumental errors.