High precision dual line leveling

The aim of this article is to investigate the accuracy of dual line leveling, and develop a methodology for its execution to enhance the precision of elevation determination by accounting for vertical refraction and controlling the non-horizontality of the leveling beam. Methodology. Considering that digital levels can measure distances to the rod and account for the non-horizontality of the beam and vertical refraction during measurements, we propose a method of dual line leveling. The study describes the methodology for performing dual-line trigonometric leveling using the "forward-backward" method. It takes into account vertical refraction along the observation lines. Results. To test the methods for high precision class leveling applying the Holeski method (from the middle) and dual-line leveling ("forward-backward"), we selected a section with a prolonged ascent approximately 1 km in length, consisting of 5 sections. The method was tested using a Trimble DiNi-03 electronic level over two leveling lines. The discrepancies between the elevations obtained from the sections using the "from the middle" and "forward-backward" methods meet the requirements for high precision class leveling. The maximum discrepancy in the sections between the leveling methods was 0.42 mm. And it was 0.06 mm for the entire leveling route, 1,142 meters long. Originality. The paper considers the theoretical justification and experimental studies on the possibility of applying dual line leveling for high precision class observation programs and introducing a correction for vertical refraction on prolonged slopes. It is confirmed that the method of dual line leveling using the "forward-backward" method can be used for high precision class leveling by the "from the middle" method on prolonged slopes and has several advantages over it.