A GNSS Multibaseline Single-Epoch Millimeter-Level Positioning Method for Construction Survey of Superhigh-Rise Buildings

Abstract

When global navigation satellite systems (GNSS) are applied to construction survey of superhigh-rise buildings, satellite signal obstruction and multipath effects reduce the number of usable observations and make it difficult to obtain positioning with high precision. Considering that construction surveys are often temporary and there is structural displacement during construction, a fast or even single-epoch kinematic positioning with accuracy up to millimeter-level is necessary. In this paper, a GNSS multibaseline single-epoch millimeter-level positioning method (MSM) is proposed with zero ambiguity-closure difference (ZAC) validation, baseline length constraints, baseline vector closure constraints and coordinate adjustment to improve fixing rate and positioning accuracy. First, ambiguity-based multiple fault detection and exclusion (AM-FDE) method is proposed to detect multipath effects affecting the determination of multiple baselines, and constraints of baseline length are used to improve performance of fixing rate in the construction environment. Then, multiple baselines consisting of multiple rovers and base stations with more measurements, as well as the geometric closure constraints are used to improve positioning accuracy. Finally, known baseline length and zero baseline vector closure difference (ZBC) are used to validate the fixed solution, which improve the reliability of single-epoch positioning. A GNSS survey experiment was conducted on a superhigh-rise building at the construction height of about 90 m. The experimental results show that fixing rate of MSM is close to 100%, and positioning accuracies reference to the widely used total station in East, North, Up (ENU) components are 4.4 mm, 4.6 mm, and 8.1 mm, respectively. The MSM method can achieve a single-epoch millimeter-level positioning reference to total station in both horizontal and vertical components. Additionally, GNSS positioning error will not increase with a higher construction height, as well as GNSS can realize automatic and all-weather positioning, which has great advantages for construction survey of superhigh-rise buildings.