Method Of Weak Wake Detection In SAR Images

The technique of using Synthetic Aperture Radar(SAR)to detect and monitor sea ships and their wakes has received considerable attention in the field of marine remote sensing,and has become one of the most important applications of SAR.In view of the advantages of all-weather,all-weather and high resolution of synthetic aperture radar,its application in ship wake detection can not only achieve macro,long-term,real-time observation of the ocean,but also help to effectively extract ships Target information.However,due to the influence of sea conditions and ships,the wake is often not clearly visible in the SAR image,which makes it difficult to detect,which has a great impact on the monitoring and management of ships,so it is weak It is necessary to detect the wake.The main direction of this paper is to study the weak wake detection methods of sea ships in SAR images.Based on the sea SAR imaging,the paper discusses two typical SAR image wake detection methods: Radon transform and Hough transform,and uses two methods Respectively completed the detection of the wake of the sea surface ship.Finally,the method of detecting weak wakes of ships in complex sea surface is studied: the method of combining morphological component analysis and morphological image processing,and the feasibility of this method is verified using simulation and real wakes,respectively.The thesis mainly includes the following work:1.Based on the understanding of the basic theory of SAR imaging,the principles of synthetic aperture radar imaging and sea surface ship wake imaging are discussed.According to the classification of wake types in SAR images,the generation mechanism and geometric characteristics of various types of wakes are discussed respectively.Then,according to the principle of wake imaging,the ship's Kelvin wake is simulated,and the simulated wake is combined with the sea surface to analyze the effects of different wind speeds and ship speeds on the wake.2.Starting from the generation and influencing factors of ship's wake,discuss the method of ship's wake detection in SAR images in detail.Based on the geometric features of ship wakes in SAR images,two classic linear feature detection algorithms,Radon transform and Hough transform,are introduced.And on this basis,the normalization method of the knot and image grayscale is used to test the wake detection in the actual sea SAR image.Finally,the characteristics of the two methods in wake detection are compared and analyzed.3.Aiming at the sea clutter,it will cover the sea wake and weaken the wake characteristics,resulting in the problem that the ship's weak wake cannot be effectively detected under complex sea conditions.Introducing the morphological component analysis method,using its unique sparse representation of different morphological components,the sea surface SAR image is separated from the sea surface texture and the structural characteristics of the ship's wake to achieve image preprocessing,here Based on the combination of morphological image processing methods,the separated wake structure is finally enhanced to finally enhance the weak wake feature,and finally the Radon transform is used to detect the processed wake.Based on this theory,the weak wakes of simulation and actual ships were tested and analyzed,which verified the feasibility of the method.