An evaluation of skylight polarization patterns for navigation.

Tao Ma,Yujie Wang,Zhiwen Xian,Junxiang Lian,Xiaoping Hu,Lilian Zhang,Xiaofeng He

doi:10.3390/s150305895

Tao Ma, Yujie Wang + Show 5 more

Open Access

https://doi.org/10.3390/s150305895

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Abstract

Skylight polarization provides a significant navigation cue for certain polarization-sensitive animals. However, the precision of the angle of polarization (AOP) of skylight for vehicle orientation is not clear. An evaluation of AOP must be performed before it is utilized. This paper reports an evaluation of AOP of skylight by measuring the skylight polarization patterns of clear and cloudy skies using a full-sky imaging polarimetry system. AOP measurements of skylight are compared with the pattern calculated by the single-scattering Rayleigh model and these differences are quantified. The relationship between the degree of polarization (DOP) and the deviation of AOP of skylight is thoroughly studied. Based on these, a solar meridian extracted method is presented. The results of experiments reveal that the DOP is a key parameter to indicate the accuracy of AOP measurements, and all the output solar meridian orientations extracted by our method in both clear and cloudy skies can achieve a high accuracy for vehicle orientation.

Highlights

Navigation is a critical and difficult issue in many applications for autonomous vehicles
The desert ant Cataglyphis bicolor, for example, is able to utilize the skylight polarization pattern as a compass to forage for meters and return back to its nest on a straight line [1]
We focus on the evaluation of angle of polarization (AOP) and degree of polarization (DOP) patterns of skylight, and the following two characteristics of the polarimetry system are taken into consideration in the calibration: (1) the measured reduced Mueller matrix of the fish-eye lens by the method in [25]; (2) the distortion of the fish-eye lens according to the calibration toolbox for Matlab [28,29]

Summary

Introduction

Navigation is a critical and difficult issue in many applications for autonomous vehicles. Many animals can utilize the natural polarization patterns for navigation. The desert ant Cataglyphis bicolor, for example, is able to utilize the skylight polarization pattern as a compass to forage for meters and return back to its nest on a straight line [1]. A range of marine animals, such as fishes and mollusks, can perceive the polarization of light, and use it for orientation and navigation [2]. Dung-beetles can perceive the moonlight polarization patterns [3]

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Conclusion