How to get navigation information within patches of sky as insects do?: A primitive orientation by skylight polarization maps

Many insects can derive navigation information from skylight polarization within patches of sky. The current methods simulating insect strategy take advantage of the skylight polarization through single numerical values rather than patterns. In this paper, we present a method to get navigation orientations by gradient vectors of skylight polarization maps even if the Sun is invisible or occluded by clouds. The maps are provided by a zenith centered imaging polarimeter with narrow field of view. Navigation orientations can be worked out by the combination of solar azimuths and calendar. We can gain additional insights into the navigation behavior of insects via the experiments.