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Color channel selection is essential for accurate segmentation of sky and clouds in images obtained from ground-based sky cameras. Most prior works in cloud segmentation use threshold-based methods on color channels selected in an ad hoc manner. In this letter, we propose the use of rough sets for color channel selection in visible-light images. Our proposed approach assesses color channels with respect...
Fine-scale short-term cloud motion prediction is needed for several applications, including solar energy generation and satellite communications. In tropical regions such as Singapore, clouds are mostly formed by convection; they are very localized, and evolve quickly. We capture hemispherical images of the sky at regular intervals of time using ground-based cameras. They provide a high resolution...
Ground-based Whole Sky Imagers (WSIs) are now commonly used for cloud observations. Upon deployment, they may not be exactly level or precisely face north. This significantly affects subsequent processing of the images, especially for applications where two or more imagers are required, e.g. 3D volumetric cloud reconstruction. We present a method to remove this mis-alignment using the sun position...
Ground-based whole sky imagers (WSIs) can provide localized images of the sky of high temporal and spatial resolution, which permits fine-grained cloud observation. In this paper, we show how images taken by WSIs can be used to estimate solar radiation. Sky cameras are useful here because they provide additional information about cloud movement and coverage, which are otherwise not available from...
Fine scale cloud monitoring using ground-based imagers is becoming popular for a variety of applications and domains. We present a framework for cloud base height estimation using two such imagers; our method is based on stereoscopic scene flow. We demonstrate the feasibility of our approach and use computer-generated images with controlled cloud height to validate the accuracy of our method.
Ground-based whole sky imagers are popular for monitoring cloud formations, which is necessary for various applications. We present two new Wide Angle High-Resolution Sky Imaging System (WAHRSIS) models, which were designed especially to withstand the hot and humid climate of Singapore. The first uses a fully sealed casing, whose interior temperature is regulated using a Peltier cooler. The second...
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