Effect Of Environmental Factors And Latitude And Longitude Difference On The Sky Polarization Mode

The sky polarization mode contains the location information for polarization navigation,which plays an important role in the realization of polarization navigation.The sky polarization mode is formed by various internal and external factors such as atmospheric mode,gas molecules,aerosols,clouds,ground surface,time,and geographic location when sunlight passes through the atmosphere.And different factors lead to certain differences.Therefore,it is particularly important to establish a theoretical model that is closer to the actual atmosphere for simulation analysis,and to conduct quantitative testing research on the sky polarization mode in the actual environment.In order to study the effect of different factors on the sky polarization mode,analyze the direction information of polarization navigation in the actual atmospheric environment.In this paper,re-developed lib Radtran software is used to simulate and analyze the effect of environmental factors and longitude and latitude changes on the sky polarization mode.Meanwhile,synchronous off-site testing is carried out in the actual environment,and analyzes the effect of environmental factors and the difference of latitude and longitude on the sky polarization mode quantitatively.Firstly,Starting from the atmospheric radiation transmission theory,this paper introduces the formation mechanism of sky polarization mode and its main effect factors.Explains the simulation principle of the sky polarization mode.By using the MYSTIC vector radiation transfer model of Monte Carlo method,calculates the atmospheric vector radiation transfer process.Explains the Stokes vector method of sky polarization mode and its test principle.And sets up the image-based sky polarization mode test system.Secondly,this paper studies effect of cloudiness on the sky polarization mode.Tests and analyzes the effects of different cloudiness on polarization degree,neutral point identification,polarization azimuth and solar meridian extraction.The results show that the polarization degree decreases with the increase of cloudiness,when the cloudiness is less than 10%,the polarization degree and polarization azimuth distribution law is obvious,and the neutral point area can be identified and the solar meridian can be extracted.When the cloudiness is 91%,the polarization azimuth symmetry distribution is disturbed,and the solar meridian is distorted and deviated,so it cannot be extracted.However,the circular distribution of the polarization degree still exists,and the actual neutral point position can be identified.Besides,this paper studies effect of surface albedo on sky polarization mode.Simulates and analyzes the effect of different surface albedo and different surface types on the polarization degree and polarization azimuth.And the actual tests are carried out on grassland,ocean and asphalt surface respectively.The results show that the surface albedo has a attenuation effect on the polarization degree value,on the same day and the same time,the greater the surface albedo,the smaller the maximum polarization degree value;the greater the difference of surface albedo,the greater the average reduction of maximum polarization degree value,and the greater the reduction range of maximum polarization degree value.The surface albedo has basically no effect on the polarization azimuth.Finally,this paper studies effect of longitude and latitude difference on sky polarization mode.Simulates and analyzes the effect of latitude and longitude changes on the direction of the solar meridian.And the actual tests are carried out in different places respectively.The results show that the effect of longitude changes on the direction of the solar meridian is greater than that of latitude changes.On the same day and the same time,the greater the longitude and latitude,the greater the solar azimuth;the greater the difference in longitude and latitude,the greater the difference range of solar azimuth.The rotation angle of the solar meridian at the two test locations is different during each test period.The rotation angle of the solar meridian increases first and then decreases at each fixed time of the day.