Abstract Webcams and automated, color photography cameras have been routinely operated in many U.S. national parks and other federal lands as far back as 1988, with a general goal of meeting interpretive needs within the public lands system and communicating effects of haze on scenic vistas to the general public, policy makers, and scientists. Additionally, it would be desirable to extract quantifiable information from these images to document how visibility conditions change over time and space and to further reflect the effects of haze on a scene, in the form of atmospheric extinction, independent of changing lighting conditions due to time of day, year, or cloud cover. Many studies have demonstrated a link between image indexes and visual range or extinction in urban settings where visibility is significantly degraded and where scenes tend to be gray and devoid of color. In relatively clean, clear atmospheric conditions, clouds and lighting conditions can sometimes affect the image radiance field as much or more than the effects of haze. In addition, over the course of many years, cameras have been replaced many times as technology improved or older systems wore out, and therefore camera image pixel density has changed dramatically. It is shown that gradient operators are very sensitive to image resolution while contrast indexes are not. Furthermore, temporal averaging and time of day restrictions allow for developing quantitative relationships between atmospheric extinction and contrast-type indexes even when image resolution has varied over time. Temporal averaging effectively removes the variability of visibility indexes associated with changing cloud cover and weather conditions, and changes in lighting conditions resulting from sun angle effects are best compensated for by restricting averaging to only certain times of the day.

中文翻译：

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使用摄像头监测能见度障碍

摘要 早在 1988 年，美国的许多国家公园和其他联邦土地就经常使用网络摄像头和自动彩色摄影相机，其总体目标是满足公共土地系统内的解释需求，并将雾霾对风景的影响传达给公众。公众、政策制定者和科学家。此外，希望从这些图像中提取可量化的信息，以记录能见度条件如何随时间和空间变化，并以大气消光的形式进一步反映雾霾对场景的影响，而不受时间变化的照明条件影响日、年或云量。许多研究表明，在城市环境中，能见度显着下降且场景往往是灰色且没有颜色的，图像指数与视觉范围或消光之间存在联系。在相对干净、清晰的大气条件下，云和光照条件有时会影响图像辐射场，甚至比雾霾影响更大。此外，多年来，随着技术改进或旧系统老化，相机已被多次更换，因此相机图像像素密度发生了巨大变化。结果表明，梯度算子对图像分辨率非常敏感，而对比度指数则不然。此外，时间平均和一天中的时间限制允许在大气消光和对比度类型指数之间建立定量关系，即使图像分辨率随时间变化。时间平均有效地消除了与云层和天气条件变化相关的能见度指数的可变性，并且通过将平均限制在一天中的特定时间来最好地补偿由太阳角度效应引起的照明条件变化。