Fig. 6

Variation trends of the measurement error in trigonometric leveling using the intermediate station method under different observation conditions. Subplots (A) to (F) correspond to horizontal distances ranging from 100 m to 600 m (at 100 m intervals), illustrating the relationship between vertical angles \(\:\alpha\:\), \(\:\beta\:\), and the measurement error \(\:{m}_{{h}_{12}}\).