Confocal Ellipse Hough Transform for Polarization Compass in the Nonideal Atmosphere

The polarization compass is an autonomous, long-endurance compass technique that is intended for enhancing the environmental suitability of the integrated navigation systems. Numerous studies on polarization compass are based on the single Rayleigh scattering model. However, the real atmosphere is usually nonideal and does not conform to the ideal single Rayleigh scattering model. The single Rayleigh scattering model would have a constant error in a nonideal sky with a certain partial cover. Compared with the single-scattering model, Hannay’s model with multiscattering equations provides a better description of the polarization pattern in the real atmosphere. Thus, the ellipse Hough transform (EHT) algorithm is proposed in this study to extract neutral points from the polarization pattern based on Hannay’s model to correct the error mentioned above. To prove the effectiveness of the EHT algorithm, several experiments have been carried out in the nonideal sky. Also, experiment results show that the average error of solar zenith and azimuth angle of the Hough transform (HT) is less than 1° in nonideal weather with 30% cover. In conclusion, the EHT improves the accuracy of the polarization compass by 50% in multiscattering light with a partial coverage of the sky and enlarges the environmental suitability of the polarization compass.