| ECDIS (Electronic Chart Display and Information System) is important navigation equipment, which is significant for ships navigation. Radar is also important for navigation. It can not only detect the fixed targets such as islands and coastlines, but also the moving targets. Radar overlays on the ECDIS can improve the navigation accuracy, which is significant for avoiding collisions as well. This paper takes all the pragmatic factors into account, and designs and realizes the whole overlay system.First of all, the paper introduces the ECDIS and the radar theory. Then the structure of the system is designed based on these theories. And the design principles, requests and the difficulties are discussed. At last, the proper scheme of the system is designed.The pre-processing of radar signal is one of the difficulties. Based on radar constant false alarm rate (CFAR) theory, after analyzing several kinds of sea clutter model and researching various kinds of CFAR detector, this paper proposed a proper sea clutter removal scheme. Moreover, a new sea clutter removal method which combines the adaptive signal processing and blind source separation is proposed in this paper. The advantage of this method is that it requests no prior knowledge of sea clutter, which makes the method more adaptive. Through the simulation and experiment, the new method has good performance.In the last part of this paper, the radar overlay ECDIS system is realized by DirectX programming, which has two advantages: the drawing of radar image is done in the display memory, which requests no modification of ECDIS program; the computer memory and the display memory are working simultaneously, which improves the speed of the whole system. At the same time, the system has good display performance. |
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