Design of Spatial Filter for Water Level Detection

This paper proposes an optimization procedure of a spatial filter in a water level detection system. The water level of running water of a river is detected by applying a temporal filter and a spatial filter to a video of various river scenery. Previously, we have proposed an algorithm based on “addition” of frames and “horizontal” detection of edges. We have confirmed its superiority to the existing method based on “subtraction” of frames and “vertical” detection of edges, especially when the scenery contains rain or snow drops. However, its detection performance is limited since coefficients of the edge detector are fixed. In this paper, we propose a design method of a spatial filter as a general form of the edge detector so that the system becomes flexible to change of the river 2 scenery. Optimization criterion is proposed and the filter coefficients are determined for each of the river scenery. It is confirmed that the proposed method reduces the standard deviation of the detection error by 4.4 [%] and 7.6 [%] comparing to the conventional horizontal Prewitt filter and the horizontal Sobel filter, respectively.