What is it about?

SkyPole is a method for locating True North and locating the observer’s LATITUDE on the planet using the polarization patterns of daylight. Humans have developed multiple forms of navigation to locate True North, but these methods encounter weaknesses that limit their usefulness. Animals, on the other hand, such as birds and insects, developed navigation methods based on sparse magnetic and visual cues. Stéphane Viollet and colleagues present a bio-inspired method called SkyPole for using the polarization of daytime light as a cue for determining the North Celestial Pole and thus the observer’s latitude on the planet.

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Why is it important?

Daylight is polarized as it scattered by small particles present in the atmosphere. The sun’s path through the sky rotates around the north celestial pole making the pattern of polarization (degree of polarization) rotate around this point as well. By collecting images of daylight polarization over time with a polarimetric camera, skypole can find the north celestial pole from at least three of these images and the intersection of time-invariant polarization lines.


SkyPole requires a long data collection time and may not be suitable for instantaneous global positioning, although it may provide insight into animal navigation methods and may provide an alternate global positioning methods in areas in which GPS satellite signals are inaccessible.

Stéphane Viollet
Centre National de la Recherche Scientifique

Read the Original

This page is a summary of: SkyPole—A method for locating the north celestial pole from skylight polarization patterns, Proceedings of the National Academy of Sciences, July 2023, Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2304847120.
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