基于高速公路视频图像的能见度计算

能见度作为重要的气象观测因素之一，影响高速公路行车安全.基于视频资料的能见度计算方法类似于人眼的感知方式，具备对恶劣天气条件和复杂场地的适应性.基于安徽省2016年10月17日、12月1日和7日的3次大雾天气过程，选取跨省分布的3个高速公路站点，使用对应时次下视频图像灰度值均方差与能见度观测值建立计算模型.结果表明：1）随着大雾天气过程变化，模型计算结果较好体现了能见度的变化规律，对高速公路行车具有指导意义；2）基于视频图像的能见度计算方法类似于人眼观测，能见度越高，人眼分辨地物清晰度越高，图像均方差越大；3）由于监测原理和环境差异，能见度测量值与模型计算结果之间存在误差，理论上大雾空间分布越均匀，能见度仪和监控摄像头距离越近，计算误差越低.

Visibility calculation algorithm based on highway video image

Visibility is one of the important meteorological factors, and low visibility affects the safe and efficient operation of expressway. Visibility calculation method based on video data is similar to the perception of human eyes, and has the adaptability to bad weather conditions or complex observation sites. Based on three weather processes of fog in Anhui province on October 17th, December 1st and 7th of 2016, the visibility calculation model were built by using gray mean square error of corresponding video image and visibility observation data of three highway sites in Anhui province. Results show that the modeled visibility can well reflect the actual visibility corresponding with the change of fog process. The proposed visibility calculation method based on video image is similar to the perception of human eyes, i. e., the higher the visibility, the higher the resolution of terrain features for human eyes, and the greater the variance of the monitoring image as well. However, due to the difference in monitoring principle and the environment properties, error exists between the observation data and the calculated results. Theoretically, the error is low under the conditions of fog with uniform spatial distribution, and the visibility meter being close to the surveillance camera.