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

Area of Science:

• Atmospheric optics
• Navigation systems
• Optical sensing

Background:

• Skylight polarization patterns offer directional cues for navigation.
• Maritime navigation faces challenges like vessel tilt, clouds, and obstructions.
• Existing navigation systems may fail in GPS-denied scenarios.

Purpose of the Study:

• To develop a gyro-stabilized polarization imaging system for maritime navigation.
• To create a robust algorithm for polarization compass orientation.
• To address interference and obstructions in polarization-based navigation.

Main Methods:

• Developed a gyro-stabilized division of focal plane (DOFP) polarization imaging system.
• Implemented a polarization compass algorithm with coordinate transformations.
• Utilized neutral point detection and solar meridian extraction for accuracy.
• Conducted field experiments in the South China Sea.

Main Results:

• Optimal polarization detection found in the 450-500 nm spectral range.
• Achieved a root mean square error (RMSE) of 0.639° and MAD of 0.541° compared to GPS+IMU.
• Demonstrated robustness against vessel motion and partial sky obstruction.
• Observed diurnal variations in degree of linear polarization (DOLP) and angle of linear polarization (AOLP).

Conclusions:

• The developed system and algorithm provide accurate and reliable maritime navigation.
• Polarization imaging is a viable alternative for navigation in GPS-denied environments.
• This research advances optical sensing for robust maritime applications.