Research On Detection Method Of The Small Targets At Sea

Synthetic Aperture Radar(SAR)is a kind of active microwave imaging radar with high resolution.It has the advantages of all-day and all-weather work,these characteristics make SAR become the important technical of the marine target detection application.The detection research for the marine weak&small target is an important branch in the field of marine target detection.It has been become an important research direction in SAR applications in recent years.The traditional target detection method is the constant false alarm rate(CFAR)detection method,which relies on the distribution of background clutter and the contrast between target and background clutter.With the increase of SAR image resolution,the traditional clutter distribution model is no longer applicable,which leads to the failure of traditional CFAR detection method.In addition,due to small radar cross section(RCS)of the target and low signal-to-clutter ratio(SCR),which resulting small target cannot be effectively detected.In view of the above problems,this paper research in the following aims at small target detection in SAR image which has low SCR:1)We analyze the causes of low visibility of small targets from the aspects of target factors,SAR sensor factors and environmental factors of sea clutter,the basic detection framework of small target is given here;2)In the aspect of enhanced preprocessing,we propose a SCR enhancement method based on wavelet multi-scale selective fusion according to the target and background distribution characteristics between wavelet sub-bands.In this process,we firstly decompose the SAR image and then selectively reconstruct the wavelet sub-bands based on the correlation of the target,and then product the every reconstructed components,all the fusion operation can improve the SCR of SAR image;3)In the aspect of small target detection,we firstly describe the basic principle of CFAR method and describe a classical method based on local threshold segmentation,to describe the effect of SCR enhancement on target detection result,we propose a detection method based on enhanced SAR image.Experimental results show that the proposed SCR enhancement method can significantly improve the SCR of SAR images,and the detection method proposed in this paper can be effectively detect the small target in SAR image.