Cloud Detection Method Based on All-Sky Polarization Imaging

Abstract

Sky cloud detection has a significant application value in the meteorological field. The existing cloud detection methods mainly rely on the color difference between the sky background and the cloud layer in the sky image and are not reliable due to the variable and irregular characteristics of the cloud layer and different weather conditions. This paper proposes a cloud detection method based on all-sky polarization imaging. The core of the algorithm is the “normalized polarization degree difference index” (NPDDI). Instead of relying on the color difference information, this index identifies the difference between degree of polarization (DoPs) of the cloud sky and the clear sky radiation to achieve cloud recognition. The method is not only fast and straightforward in the algorithm, but also can detect the optical thickness of the cloud layer in a qualitative sense. The experimental results show a good cloud detection performance.

Three-dimensional model of cloud layers based on all-sky polarization imaging data

“…The computer can calculate real-time difference of all-sky polarizing patterns. As mentioned by Wunan 7 , NPDDI can clearly show the strong contrast of the boundary of clouds.…”

“…However, the data in the images could also be lost. Our previous studies developed a normalized value NPDDI to illustrate the bandage of clouds 7 and overcame the above shortcomings. NPDDI values could acquire effetely from DoP values.…”

Automated Nighttime Cloud Detection Using Keograms When Aurora Is Present

“…At optical wavelengths, low‐cost cameras may be used by solar power station operators who want an automated method for estimating or forecasting power generation (Alonso‐Montesinos, 2020). Daylight polarization can be used to determine clear sky versus cloudy sky, and the optical thickness of the cloud layer, if present (W. Li et al., 2022). A number of researchers have successfully developed methods for sorting cloud data automatically using the red and blue intensity relationships of all sky images, total sky imagers, or whole sky cameras (Q. Li et al., 2011; Long et al., 2006).…”

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

“…Skylight polarization has recently been receiving growing interest for several fields, such as cloud detection [1], realistic rendering of outdoor scenes [2], or for bio-inspired navigation [3]. Sunlight is scattered by the atmosphere.…”