Patent US 6,098,029

The present invention has an object to measure the height of a liquid surface automatically by an image processing. According to the present invention, therefore, the situation over a side wall and the situation of the liquid surface in the image, as taken from an ITV camera, of the neighborhood of the liquid surface are image-analyzed to estimate the boundary position between the side wall and the liquid surface thereby to determine the position of the liquid surface on the image, and the liquid-surface position on the image is transformed from an image coordinate system to a real spatial coordinate system to determine a real position of the liquid surface.