A quick algorithm for horizon line detection in marine images

Abstract

The information about ship spatial orientation is required by different ship systems. For example, dynamic positioning, artillery, or video tracking systems, to stabilize a ship, a gun or a camera, have to work in advance, and therefore, they need the information about future ship orientation. To obtain this information, a current ship orientation and sometimes also historical orientations are necessary. Another example is ship echo-sounders applied to hydro-graphic surveys. Since each list of the ship affects echo-sounder depth measurement, to determine true depth of the sea based on the echo-sounders, the spatial orientation of the ship at the moment of each measurement has to be known. One method for determining the ship spatial orientation is an optical system including video cameras, a computer and specialized software. The system works through extracting the horizon line from each video shot and calculating an angle between the line and the horizontal border of the shot. The main disadvantage of this approach is its slowness. There are a number of methods which can be used to extract the horizon line from an image; however, they are so computationally complex that their application to high-resolution images is limited rather to only post-processing. In the paper, a quick method for horizon line detection is proposed. The experiments on real marine images showed that it is at least as accurate as other methods, what is more, it is also a number of times faster and it seems to be more reliable than its rivals.