Annotation

According to the results of geometric leveling, i.e. «from the inside» and «forward-back», those two methods were compared on the geodetic testing ground.

The studies were carried out with the South DL 202 batter level, a 32-times increase in the optic tube, and a 0.5" self-aligning projection accuracy and a set of barcode retention rails. Observations were performed under dark and changing weather conditions at 12–15 °C, with a temperature change of not more than 1 °C per hour, the image of the rails was practically calm. The average excess between the two points, based on the results of leveling «from the inside» method, is 12,2877 mm, and in case of the «forward-back» method, it is 12.2884 mm, while the difference between those values is 7.7 mm. It is found that the accuracy of leveling in the «forward-back» method, without taking into account the vertical refraction, corresponds to the accuracy of the leveling «from the inside». There are observed advantages of the «forward-back» method, i.e. it is an opportunity to control the position of the visor beam in the process of leveling and simplify the selection of alignment lines.

Analyzing the accuracy of determining of the excess with the «from the inside» method and the «forward-back» one, the authors of the work note that the errors, caused by the accuracy of the counting, are the same for the leveling section (150 m), and the error of setting of the beam of leveling in horizontal position and for vertical refraction will enter the average excess in times less than for the leveling method «from the inside».

Having studied the data of observations in two ways, it is worth noting that the methods of geometric leveling «forward-back» and leveling «from the inside» are almost of the same accuracy. In the method «from the inside», the number of leveling stations is almost 2 times less than in the «forward-back» method. The «forward-back» method greatly simplifies the leveling process by setting the leveling line (leveler).

The «forward-back» method, unlike the «from the inside» one, allows controlling of the position of the beam of a leveling visor by calculating the value of the total non-horizontal angle ε" (recommended for digital levels).

In order to reduce the effect of refocusing of the focus tube in the «forward-back» method, it is proposed to start leveling at the next station from the leveler, at which the leveling was completed at the previous station.