DETERMINING ACCURATE ICE COVERAGE ON DANUBE BY WEBCAMERAS
Authors:   National University of Public Service, Keve Gábor 
Published: November 2020

For most Hungarian rivers, especially the Danube, floods and other damages caused by ice have produced and are producing serious problems. Meanwhile, the number of national researches on ice that improve the effectiveness of ice protection is low, and technical development is not significant at this point. The main focus of the research presented in this article emphasizes the advancement of this research and to the further develop of the river ice monitoring methodology. The key objectives are listed in the following points: Develop a fast, automated, cost effective, and continuous ice-collection method based on web camera images with a precision far beyond their manual or estimation procedures. Verification of the developed solution through error analysis. Solutions that do not require specialized software were preferential. Analyze the time pulsation and daily travel curve of the ice jam coverage ratio of the Danube with the developed high frequency measurement process. The aim of this paper is to promote modernization of the Hungarian ice-observations and to provide a numerical basis for scientific research related to this topic. I have demonstrated that the web-based, automated river ice-monitoring system can be used as a detailed hydrographic tool and can provide more accurate results than the currently used estimation or manual image processing methods. I have proved that from the images of webcams to determine the rate of ice coverage, it is enough to imagine the views of the cameras in advance, with a single spatial perspective transformation, it is not necessary to use georeferencing, orthorectification, or complicated form recognition procedures for each frame. From the perspective mapping, the aspect ratio of the pixels (pixels) to the water surface in the image being examined can be calculated, and it is sufficient for the computation of ice coverage in all images with the same viewpoint. By doing this, I've narrowed the task to the grading of the water-ice pixels. A simple numerical method was developed and verified to determine the area ratio of pixels to the surface of the water. I have developed an automatic, adaptable threshold value, which distinguishes between ice and water with appropriate precision as picture points (pixels). With my method of ice coverage determination, I observed significant temporal pulsation and daily periodicity in the ice movement of the observed Danube reach. I have found that the small number of daily estimates are not representative to determine daily average ice coverage. I recommend continuous webcams monitoring. The new findings contribute to a more accurate understanding of the spatial and temporal structures of ice floes in rivers, as well as the methodological development of their measurability and reproducibility. My work creates the basis for the modernization of the Hungarian ice-monitoring network. The operation of such a network provides the condition that in the future on the larger rivers ice floe forecasting and alarm systems may be established. The time series collected over the past decades provide data for national research on river ice phenomenon’s too.