INFLUENCE OF THE REFRACTION ON THE ACCURACY OF GEOMETRIC LEVELING
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Keywords:
geometric leveling, refraction, level, leveling rod, air temperature, accuracy of measurementsAbstract
The article contains a list of references and scientific articles that investigate the accuracy of geodetic measurements, the problems of errors, as well as factors affecting the accuracy and the possibility of taking them into account when conducting various geodetic works. External and internal factors are described. influencing the accuracy of geodetic measurements. The main part of the article describes the essence of geometric leveling. Characteristic for geometric leveling is that the sighting beam along its entire length does not pass at the same height from the ground surface. This means that the sighting beam passes through air layers of different temperature and density. This, in turn, affects the accuracy of measurements. The article presents the assumption of the French astrophysicist Andre Lallemand that the temperature of the air changes in an arithmetic progression, while the height above the ground level changes exponentially. Professor Krasovsky F.N. proposed a technique that states that refraction increases in proportion to the square of the distance from the level to the slats. The scheme of the spreading of the sighting beam horizontally and the refraction curve is shown. The studies carried out by Krasovsky have shown that the refraction is minimal at the summer sunny day in the morning. It reaches its maximum values in the daytime. In the evening, before sunset, the effect of refraction is minimal. The research data on the effect of refraction on the accuracy of geometric leveling, carried out by German engineer Colmyuller, are presented. They confirm the results obtained by Professor Krasovsky. As conclusions, it was concluded that for more accurate geometric leveling, measurements are best done in the morning, and the distance from the level to the staff should not exceed 60 meters. Also Andre Lallemand recommends that at each station measure the air temperature at the height of the sighting beam near the slats and near the lens of the level. Although Professor Krasovsky does not recommend introducing this amendment into the calculation formula.
References
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