Real-time maritime skylight polarization pattern measurement and robust polarization navigation

Skylight polarization patterns, generated by sunlight scattering in the Earth's atmosphere, serve as an under-utilized source of directional information for navigation. This study addresses the challenges of maritime polarization navigation, including vessel tilt, cloud interference, and structural obstructions, by developing a gyro-stabilized division of focal plane (DOFP) polarization imaging system and a robust polarization compass orientation algorithm. The system captures high-resolution polarization images across multiple spectral bands (410-870 nm), with optimal polarization detection identified in the 450-500 nm range. Our algorithm compensates for vessel motion through real-time coordinate transformations and employs a dual-feature recognition approach combining neutral point detection and solar meridian extraction to maintain measurement integrity under partial sky obstruction. Field experiments conducted in the South China Sea demonstrated that the system achieves a root mean square error (RMSE) of 0.639° and a mean absolute deviation (MAD) of 0.541° when compared to GPS + IMU reference data. Temporal analysis revealed significant diurnal variations in degree of linear polarization (DOLP) and angle of linear polarization (AOLP) distributions, with maximum DOLP values ranging from 0.28 at midday to 0.48 during dawn/dusk periods. This research advances polarization-based optical sensing for maritime applications and offers a promising solution for interference-resistant navigation in GPS-denied environments.