The Simulation And Inversion Of Ship Wakes Polarized SAR Images

The main purpose of simulation and inversion of ship wakes images using polarized SAR(Synthetic Aperture Radar)is to acquire and process wakes information,so as to realize the detection,identification,classification and tracking of ocean moving targets.It is a great significance in the detection and monitoring of marine environment and also provides a theoretical basis for the advancement of the national marine military power strategy.The related theoretical overview of ship wakes polarized SAR imaging,the establishment and solution of the mathematical models of ship wakes and rough sea surface,and the simulation of ship wakes polarized SAR images,and the processing and detection of real images are studied in this present dissertation based on polarized theory,slender body theory,fluid mechanics theory,the wave spectrum model,the multiplicative speckle noise theory,the mathematical morphology images processing method,as well as linear inversion algorithm.The main contents are as the following:1.The theoretical basis of polarized SAR imaging is reviewed.Firstly,from the concept of polarized and synthetic aperture,the operation principle and imaging principle of polarized SAR is expounded in this paper.Secondly,by comparing the images,the most important difference between ship wakes optical images and polarized SAR images is given,which is speckle noise characteristic.Finally,the classification of ship wakes and the different types of ship wakes polarized SAR imaging mechanism are briefly discussed in this paper based on the wake wave scattering theory and wave modulation theory.2.The mathematical model of ship wakes and rough sea surface based on the theory of speckle noise are established and solved.Firstly,according to the theory of ship slender body,fluid mechanics and other related theories,the ship wakes wave height model is established.The model is used to simulate the wake of five different types of ships at the same speed and the wake wave height of the same ship at different speeds.The effects of ship geometric dimensions and ship speed on the one-dimensional,two-dimensional and three-dimensional results of ship wake are analyzed.Secondly,the rough sea surface model according to the PM wave spectrum theory is established.Using FFT(Fast Fourier Transform)and IFFT(Inverse FFT),the model is solved to give the the simulation results of rough sea surface under different air velocity conditions,and the characters of rough sea surface at different wind speed are analyzed.Finally,the composite rough surface model which combines wave height model and rough sea surface model,and then by using the mathematical model of speckle noise,the functional simulation of the ship wakes polarized SAR images is realized.3.The ship wakes polarized SAR images detection and parameter inversion are carried out.Firstly,using mathematical morphology to process ship wakes polarized SAR images,such as noise-suppressed,expansion and corrosion processing,as well as edge extraction could retain the important information of ship wakes.Secondly,using two linear inverse algorithm to do change detection on the ship wakes images after the end of the images pretreatment,and detection results of the two algorithms is evaluated.Finally,by using pixel coordinates of the pixel length in MATLAB,the inversion results of wave length of ship wakes and speed of ship are carried out.The inversion method is verified logically by analyzing the error.