Active gravity-aligned reference Axis for high-precision verticality assessment in construction

초록

Verticality and precise alignment of building components are essential for structural safety and construction quality. Conventional instruments such as Total Stations (TS), Terrestrial Laser Scanners (TLS), and Digital Levels (DL) rely on relative coordinate systems and assume level ground, making them prone to errors on uneven terrain. To address these limitations, an active reference axis device is developed to directly provide a gravity-aligned vertical reference during sensing. The device integrates a roll–pitch gimbal (RPG) with an inertial measurement unit (IMU)–based feedback algorithm for automatic alignment with the true vertical, regardless of ground inclination. ArUco marker–based pose estimation and principal component analysis (PCA)–based detection establish a stable geometric reference for point-cloud and image-derived measurements. Experiments show an average vertical deviation of ±0.09°, meeting ACI 117–10 tolerance limits. Calibrating at acquisition reduces measurement time and cost, enabling reliable verticality assessment for digital-twins and automated construction control. © 2026 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

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