Enhanced Azimuth Determination in Drilling via Piecewise Polynomial Fitting and Interpolation

Abstract

Precise geomagnetic azimuth measurement is essential for automation and intelligent operations in deep-Earth and deep-sea resource exploration. However, during drilling, the main sources of azimuth error include the inherent distortion of triaxial accelerometer and triaxial magnetometer, which requires prior calibration. To address this issue, we focus on static azimuth measurements by analyzing the error propagation relationship, developing a comprehensive error correction model, and proposing a correction method that combines piecewise polynomial fitting and improved interpolation. Finally, the proposed algorithm was experimentally validated using a high-precision inclinometer calibration platform. The experiment compared the error correction effects of the three-step combination method and the proposed method. At a confidence level of $p = 0.95$ and an axial tilt of $I = 0.594$ , dA decreased from ( $3.1^{\circ }~\pm ~0.9^{\circ }$ ) to ( $1.8^{\circ }~\pm ~0.5^{\circ }$ ) and ( $7\times 10^{\mathbf {-4}}~\pm ~3.7\times 10^{\mathbf {-2}}$ ) for the traditional and proposed method, respectively. The proposed method demonstrates good performance in azimuth reconstruction and meets the practical engineering demands of azimuth calibration in measurement-while-drilling (MWD) system.