Study On The Extraction And Application Of Solar Meridian Of The Sky Polarized Light Distribution

ky polarized light distribution pattern is an inherent attribute of nature,which canprovide a stable navigation information source for polarized light navigation.The point source polarized light test system can only obtain the local polarization information in the sky which makes the navigation sensor has the disadvantages of low accuracy and poor stability.Imaging polarized light test system can obtain the polarization information of the whole sky at the same time,which is an effective way to improve the accuracy and stability of navigation sensor.The research of polarized light navigation application based on imaging polarized light test system has become the current research hotspot.Based on the fact that the extraction accuracy of solar meridian is reduced because the least square method for fitting the solar meridian is easy to be affected by the divergence of the distribution of the feature points,and the polarized light navigation is still not applied in practice.This paper mainly studies from two aspects: establishing the method to extract the solar meridian with high precision and the method to obtain the heading angle using the solar meridian as the reference line.The specific research contents are as follows:Firstly,based on the formation mechanism of the sky polarized light distribution pattern,the Rayleigh scattering theory and Mie scattering theory are introduced,and the reference coordinate system of the sky polarized light distribution pattern is established.Based on Hough transform,the method of obtaining solar meridian is described,and the basic principle of obtaining heading angle by using solar meridian is explained.Secondly,the simulation software package of libradtran is introduced.For the problem that the low efficiency of simulation,the simulation software of sky polarized light distribution pattern is developed.An imaging polarized light test system is built,and the stability of polarization degree distribution pattern and polarization azimuth distribution pattern as navigation information source is tested and analyzed.The results show that the maximum degree of polarization of cloudy weather is much lower than that of clear weather,and the symmetry line of polarization azimuth distribution mode is still clear.Compared with the polarization degree distribution pattern,the polarization azimuth distribution pattern is more stable under the influence of weather conditions,and is more suitable for the information source of polarized light navigation.Thirdly,for the problem that the extraction accuracy of solar meridian is reduced due to the divergence of feature points in the test environment,the extraction method of solar meridian based on Hough transform is proposed.Gaussian noise is used to simulate the noise interference under the test conditions,and the solar meridian feature areas under different SNR are obtained,the performance of solar meridian extraction method based on Hough transform and the least square method fitting solar meridian under the same noise interference are simulated and analyzed.The performance of the extraction method is further compared and analyzed through the test experiment.The results show that compared with the least square method,the method based on Hough transform is more accurate.Finally,aiming at the current situation that polarized light navigation can not be applied in practice,a method of acquiring heading angle is proposed,and the experiment of acquiring heading angle is carried out,and the cause of error is analyzed.After the system error compensation,the accuracy of acquiring heading angle is within 2 °.It provides theoretical and practical reference value for the practical application of polarized light navigation.