Unpolarized sunlight becomes polarized by atmospheric scattering and produces a skylight polarization pattern in the sky,\nwhich is detected for navigation by several species of insects. Inspired by these insects, a growing number of research studies\nhave been conducted on how to effectively determine a heading angle from polarization patterns of skylight. However, few\nresearch studies have considered that the pixels of a pixelated polarization camera can be easily disturbed by noise and\nnumerical values among adjacent pixels are discontinuous caused by crosstalk. So, this paper proposes a skylight compass\nmethod based upon the moment of inertia (MOI). Inspired by rigid body dynamics, the MOI of a rigid body with uniform\nmass distribution reaches the extreme values when the rigid body rotates on its symmetry axes. So, a whole polarization\nimage is regarded as a rigid body. Then, orientation determination is transformed into solving the extreme value of MOI.\nThis method makes full use of the polarization information of a whole polarization image and accordingly reduces the\ninfluence of the numerical discontinuity among adjacent pixels and measurement noise. In addition, this has been verified\nby numerical simulation and experiment. And the compass error of the MOI method is less than 0.44 degree for an actual\npolarization image.
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