Approach to Minimizing the Influence of Changeable Observational Environment on Long-Distance Sea-Crossing Trigonometric Leveling

Abstract

Instabilities in observed environments at sea, such as the sudden appearance of fog, varying temperature or pressure, changes in wind speed and direction, and differential gravitational and magnetic fields in each observed station, will lead to fluctuating observations and difficult data processing. These factors must be considered to achieve high-precision leveling. Therefore, a sea-crossing trigonometric leveling method that satisfies the national second-order leveling accuracy is proposed according to the sources and variable characteristics of errors under the condition of lacking corresponding specifications. The procedure is described and a mathematical model is deduced in this paper. A sea-crossing leveling engineering work is used to evaluate the performance of the proposed method. The result of engineering work indicates that the proposed method can lighten the surveyor workload and improve the precision of final values to some extent compared with common trigonometric leveling methods. The method can be used in applications in which two benchmarks are far and mounting a level in the middle place is impossible, such as leveling across rivers, canyons, seas, or dense woods.