Investigation Of Skylight Polarization At Different Surface Albedo And Longitude And Latitude Based On Rayleigh Scattering Theory

Sky polarized mode is rich in location information which can provide a stable navigation resource for polarized light navigation.The sunlight is a natural source of light and the light is an electromagnetic wave.During the transmission process,electromagnetic waves are scattered and absorbed by the various atmospheric factors such as molecules,aerosol particles,clouds,geographic location,time,etc.,and due to absorption and reflection by the underlying surface,resulting in sky polarization mode.It provides prominent information of directions,solar meridian,neutral points,and polarization azimuth,these are critical in navigation.Therefore,it is imperative to establish a theoretical model closer to the actual atmosphere for simulation analysis and conduct quantitative testing research on the sky polarization mode in the actual environment.Herein,the Lib Radtran software is used to simulate and analyze the effect of different surface albedo at different surface types and the effect of longitude and latitude changed on the polarization degree and polarization azimuth.Moreover,comparative testing is carried out at the actual sites to help the theoretical studies.In this study,based on the formation mechanism of the sky polarized light distribution pattern and its main effecting factors,the Rayleigh scattering theory and Mie scattering theory are introduced.The simulation software package of Lib Radtran is introduced.The simulation principle of the sky polarization mode calculates the atmospheric radiative transfer process by using the MYSTIC algorithm of the Monte Carlo method.The Stokes vector method of sky polarization testing principle is explained.Besides,an image-based sky polarization mode test system is developed for testing.The stability of polarization degree distribution pattern and polarization azimuth distribution pattern as a navigation information source is tested and analyzed.The results show that the maximum polarization degree of a cloudy sky is much lower than that of a clear sky,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.Besides,in this study,the effect of surface albedo on sky polarization mode is tested.The effect of different surface albedo on the polarization degree and polarization azimuth at different surface types is simulated using Lib Radtran software.The actual tests are carried out on concrete,ocean,and asphalt surface correspondingly.It is found that the surface albedo has a weakening effect on the polarization degree value on the same day and at the same time.The average reduction of the maximum polarization decreases with the increase of albedo size.Furthermore,the surface albedo has no evident effect on the polarization azimuth.We also examine how longitude and latitude variations affect the polarization mode of the sky.The solar meridian’s direction is simulated and analyzed at different longitude and latitude.In addition,different cities locations are used for conducting the real investigations.According to the findings,the longitude has a more influence on the solar meridian’s orientation than latitude.The solar azimuth is increased with the increase in longitude and latitude on the same day and time,as the difference in longitude and latitude gets high the solar azimuth range gets high on the same day and time.Both sites had a distinct solar meridian rotation angle throughout each of the test periods.The solar meridian’s rotation angle rises first and then drops at each fixed hour of the day.