Analysis of the effect of turbidity on underwater target detection and recognition using 2D normalized cross-correlation
摘要
The cloudy or milky water can cause different types of physical debilitation in different contexts. The most common attenuation effects can be summarized in optical, acoustic, heat transfer, biological, chemical, communication and engineering effects. The special absorption and scattering properties of the water environment limit the detection of underwater targets and therefore make direct evaluation for image quality assessment pointless. Understanding these effects can be used to design a system that can withstand such attenuation and thus detect submerged targets. This work presents an automatic technique for detecting multiple targets immersed in water through a glass tank with increased turbidity. The targets are three Iraqi coins and a black rubber triangle. The detection procedure is performed using a normalized 2D correlation method, where the correlation between the template and the video clips is estimated and then averaged to obtain a final correlation value with extracted targets per image frame. The results show that a high recognition value was achieved for the triangle target, which is due to the high contrast with the environment and the recorded value is in the range (0.9686–0.9986). The recognition value of the coins is in the range (0.9223–0.9924) for 100 Fils coin and (0.845–0.98) for one dinar and (0.764–0.980) for 500 Fils coin. In addition to its color, the shape of the triangle with its pointed sides influences the correlation values, followed by the Iraqi 100 Fils coins with its uniform circular shape. The lowest correlation scores recorded for the one dinar and the 500 Fils coin due to their multi-sided and convex shapes respectively. The normalized 2D correlation technique achieved at final a state-of-art performance in detecting underwater targets and this can help in improving the small-scale interactions for underwater imaging systems as well as systems under controlled environments.