Inversion Technology Research Of The Marine Radar Image For Wave Height

Wave is one of the most important forms of movement of the ocean waves, and it changes periodically with the space-time. Waves can cause serious damage to the ship transportation, fishing, marine military activities, and coastal facilities, therefore, it is imperative to conduct multi-means, full-range, and real-time monitoring. Ocean wave monitoring is of great military and commercial value. Marine radar wave measuring instrument is a kind of equipment that extracts ocean wave parameters by collecting marine radar image data and with correlation method. This paper is based on the background of the research project of "ocean wave monitoring equipment" and the algorithm of X-band radar image shadow inversion of wave height. The research contents are as follows:According to the theory of electromagnetic wave scattering from random rough surface by Rune.Gangeskar, we propose to analyze the radar image data of this experiment using radar image shadow inversion of wave height. By analyzing the Rune shadow estimation results, we find that the Rune algorithm has the defects of uneven shadow segmentation, large deviation and so on. They affect the distribution of the scattered points and increase the deviation of fitting wave steepness, which directly affect the estimation precision of wave height. To solve the problem, we propose an improved algorithm that estimates wave height with shadow. Firstly, filter the same frequency interference, thinning the image, detect the edge area of radar images with edge detector. Secondly, threshold is obtained by the histogram of the edge region, and shadow region is extracted using shadow threshold. Thirdly,split shadow area using the improved adaptive segmentation method and seek shadow ratio.Finally,find the wave steep in combination with the Smith shadow function model under low grazing incidence angle, the optimal wave steepness is selected by the N-M optimal estimation principle, and effective wave height is calculated according to the definition of wave steepness. A large number of experimental data show that the accuracy of the improved experimental results is significantly improved, and it verifies the effectiveness of the improved strategy. In the fifth chapter,we put forward a new algorithm of shadow inversion based on the experimental results of the above shadow algorithm. In a fixed area where grazing angle is less than 3 degrees, shadow ratio changes with wave height. We suggest a hypothesis based on the finding above that there is a linear relationship between the wave height and ratio of shadow which is similar to the signal-to-noise ratio and wave height. Then we take experiment to verify the hypothesis. Firstly, obtain the shadow image to analyze the influence of different distance to the shadow ratio based on the above experiment background and draw the best shadow selection area. Secondly, least square model is used to fitting the relationship between the external reference height and the shadow ratio. Finally, use the fitting model to carry on the data experiment and compare the experimental data with the measured reference data. The result of the experiment is good, and it proves the feasibility and practicability of the algorithm.Finally, the estimation results by Rune, the two methods of inversion of wave heights and the true value measured by wavex are compared, and comprehensive evaluation of the performance of the three algorithms is acquired using statistical analysis.