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基于鱼眼图像修正的天空视域因子计算方法
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Abstract:
天空视域因子(SVF)是城市热环境的重要评价指标之一。利用鱼眼照片估计天空视域因子的方法快速准确，但深受等距投影的制约。在本研究中提出一种对鱼眼照片进行等距化畸变修正的方法，将任意投影模型的鱼眼镜头实拍图修正为等距投影下的图像，然后用Steyn算法计算SVF值。通过对比两组镜头的实验结果，说明非等距投影鱼眼镜头也能得到准确的SVF值，验证了该方法的精度和有效性。本文的方法具有很高的经济性、实用性，为城市热环境领域研究者及城市规划人员提供了便利。
Sky View Factor (SVF) is one of the essential indicators for urban thermal environmental assess-ment. The method of estimating SVF using fisheye photographs is fast and accurate, but it is re-stricted by equidistant projections. This study proposes an equidistant distortion correction meth-od for fisheye photographs that can transform the fisheye lens photo of any projection model into the image under the equidistant projection. Then, SVF values are calculated using Steyn’s method. Comparing the experimental results of two groups of lenses shows that accurate SVF values can be obtained for a non-equidistant projection fisheye lens. The accuracy and validity of the method are verified. The method proposed in this article is highly economical and practical, providing conven-ience for researchers and urban planners in urban thermal environments.
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