Research and Application of Trigonometric Leveling to Replace Precise Leveling

Abstract

Aiming at the low efficiency of precise geodetic leveling in tough terrain, we propose a precise trigonometric leveling (PTL) method to replace first-order Class II leveling. First, we analyze the errors of unidirectional trigonometric leveling and list corresponding ways to reduce those errors. Then, the practical formula of PTL is introduced that combines the simultaneous reciprocal observation with the leap-frog method to reduce the effect of atmospheric refraction. Besides, the PTL method uses two robotic total stations to perform an even number of reciprocal observations to avoid measuring the heights of instruments. Finally, two experiments are conducted using the PTL method; one is river-crossing precise leveling, and the other is highland precise leveling. Compared with the precise geometric leveling in the 25 km of the leveling circuit, the result shows that the standard deviation per kilometer of PTL is ±0.9 mm/km, which is less than ±1 mm/km and proves that PTL can achieve first-order Class II leveling precision to some degree conditions.