Research On Infrared Characteristics And Detection Method Of Ship Wake

Ship detection and tracking is one of the hot topics in military research.Infrared detection technology of ship wake is an effective means of sea surveillance,which identifies and tracks ship activities by detecting the heat released by the wake.Due to the attenuation of infrared radiation in the atmosphere,which is affected by the environment,an appropriate detection distance must be determined to ensure clear imaging.Additionally,the infrared wake image contains a lot of sea clutter interference,which poses great challenges to wake detection.In this dissertation,a research focused on the infrared characteristics and detection method of ship wake is conducted to address the aforementioned problems,with the models for sea surface thermal wake and Kelvin wake established.The infrared detection distance of ship thermal wake under different atmospheric conditions is calculated,and a ship wake detection method based on texture and edge features in infrared images is proposed based on the texture and edge features of wake.The detection of Kelvin wake angle and estimation of ship speed parameter are also conducted in this paper.The main research contents are as follows:(1)Research and establish models for ocean surface thermal wake and Kelvin wake.The three key stages from the formation of the ship thermal wake to its detection by infrared are analyzed,and the thermal wake buoyancy model,near-sea surface thermal wake infrared radiation model,and thermal wake infrared radiation atmospheric transmission model are established.The Kelvin wake geometry model is established based on point source disturbance theory,and the Kelvin wake wave height model is established based on the slender ship theory.The sea surface Kelvin wake dynamic infrared simulation is realized using the Unity 3D rendering engine,which provides image data support for subsequent study of wake detection method.(2)Establish the calculation model for the infrared detection distance of ship thermal wake.The attenuation effect of the atmosphere on the infrared radiation of ship thermal wake is analyzed,the variations and influencing factors of the infrared radiation during atmospheric transmission are investigated,and a calculation model for the operating distance of ship thermal wake extended source target in the infrared imaging system based on the minimum resolvable temperature difference is established.The impact of thermal wake parameters on the infrared operating distance is analyzed,and the thermal wake infrared detection distance is calculated for different atmospheric profile types and aerosol conditions.The results show that the detection distance of thermal wake is affected by thermal wake parameters,atmospheric conditions and detector performance.When meteorological conditions and thermal wake parameters are constant,the operating distance decreases with the increase of detection probability,which provides theoretical guidance for the selection of infrared detection distance of ship wake at sea.(3)Research ship wake detection method in infrared images.To address the low contrast and sea clutter interference issues in infrared images,an enhancement and detection method for ship wake images based on the combination of texture feature extraction and edge feature extraction is proposed,and the detection performance of the method is analyzed,which has a higher detection rate compared with the standard Hough transform.The Kelvin wake angle and ship heading are detected and estimated using the results of wake line extraction,and the root mean square error of ship heading is 0.38°,which confirms the accuracy of the wake extraction results.The ship speed is obtained by inverting the transverse wave length of the Kelvin wake in simulated images,and the relative error is less than 0.6%,which verifies the validity of the inversion method.