Determination of the local refraction coefficient in Cuban lateritic mineral deposits

Abstract

Much work has been done related to the characteristics of terrestrial refraction. However, very few have referred to the fluctuations of the refractive coefficient in the lower atmosphere in Cuban lateritic deposits. The objective of this research is to determine a local refraction coefficient in different climatic conditions and time of day, to increase the precision of the mineral volume calculation and to know its behavior and to analyze the influence of local refraction coefficient variations on the trigonometric leveling. The method of reciprocal simultaneous measurements of the vertical angle was applied to minimize the influence of the refractive coefficient and assess the errors committed. As results, a refraction coefficient of 0,17 was obtained, different from the 0,14 that is currently used, and that the Gaussian refraction coefficient +0,13 is not adequate to describe the refraction effects in the lower atmosphere. In conclusion, these results can be useful to better evaluate the role of refraction in topographic surveys at 1,5 m from the visual ray of the ground, in lateritic deposits on slopes greater than 20 %. The experiment on refraction showed a range of variation of KL between 0,134-0,179 near the ground on sunny days. This equates to vertical temperature gradients are 0,064-0,144 K/m during the day and 0,054 K/m after sunset.