A Stand-Alone Polarimetric Acquisition System for Producing a Long-Term Skylight Dataset

Abstract

Skylight polarization phenomenon is at the origin of a recent growing interest for bio-inspired navigation. Skylightbased orientation sensors can be simulated on the basis of physical models. In parallel, machine learning algorithms require a large amount of data to be trained. However, while some simulated databases already exists in the literature, a public database composed of real-world color polarimetric images of the sky in various weather conditions does not. In this study, a long-term experimental device is presented, designed to be left in a distant roof to acquire data over several months, using a Division-of-Focal-Plane polarization imager with a fisheye lens mounted on a rotative telescope mount. An open-source mechanical and electrical design is proposed for easy replication at other locations, with an algorithm to get the sensor's orientation and geometrical calibration in the East-North-Up frame. A sample one-month long dataset is provided on a public archive.

Passive Polarized Vision for Autonomous Vehicles: A Review

“…As a consequence, calibration efficient methods have been developed to compensate for the various errors [ 84 , 89 , 111 , 112 , 166 , 219 , 220 ]. The orientation of the camera in the inertial frame also called camera model can be determined by means of an inertial measurement unit or from solar observation for a camera equipped with a fish-eye lens [ 221 , 222 , 223 ]. A standard method used to estimate the heading relies on the fact that E-vectors are perpendicular to the sun vector leading to the calculation of eigenvalues [ 217 , 224 ].…”

“…Generating neural networks in order to detect attributes of the polarization pattern, or denoise or interpolate polarization patterns will require image databases, either generated by simulation, or acquired by polarimetric cameras [ 26 , 270 ]. These images databases are now available and will be use either to train or to validate neural networks [ 223 , 271 ] which will be relevant in robotics for processing polarimetric images in real time. Optical transform-based imaging methods will be inexpensive but will require a bank of images for calibration.…”