• Journal of the Korean Institute of Navigation
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• v.7 no.2
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• pp.1-45
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• 1983

This paper concerns the applications of the Kalman filter to navigation and the develment of computer programs of the navigational calculations. Methods to apply the Kalman filter to celestial fix, fix by cross bearing and cocked hat are proposed, and numerical simulations under various noise conditiions are conducted. The accuracy of the optimal positions obtained by the Kalman filter is compared with that of the fixed positiions by radial error method. In the case of celestial fix, an algorithm to estimate the optimal positions by using the linear Kalman filter is presented. The optimal positions by the Kalman filter are compared with the running fixes and with the most probable positions obtained from a single line of position. It is confirmed that the resutls of the proposed method are more accurate than the others. In practical piloting, bearings are generally measured intermittently and the measurement process is nonlinear. It is, therefore, difficult for us to apply the Kalman filter to fix by cross bearing. In order to be used in such an unfavorable case, the extended Kalman filter is revised and the aplicability of the revised extended Kalman filter is checked by numerical simulation under various noise conditions. In a cocked hat, an inside or outside fix is dependent only upon azimuth spread, if the error of each line of position is assumed to be equal both in magnitude and sign. A new technique of selecting a ship's position between an inside fix and an outside fix in a cocked hat by using fix determinant derived from the equation of three lines of position is also presented. The relations among the optimal position by Kalman filter, incentre (or excentre) and random error centtre of the cocked hat are discussed theoretically and the accuracy of the optimal position is compared with that of the others by numerical simulation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.547-558
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• 2008

With the advent of super cargo ship due to the explosive increase in the amount of cargo shipped via seas, some mega ports are under construction in South Korea, to accommodate the super cargo ship, and some of them already enter their final phase. To sustain the harbor tranquility, mega ports usually comprise huge vertical type breakwaters which are intrinsically vulnerable to the attack of long waves. In this rationale, we present the chamber type breakwater with a circular curtain wall - Eco-breaker 2, to alleviate the reflection of long waves and numerically investigate the hydraulic characteristics of Eco-breaker 2. As a wave driver, we use the Navier-Stokes eq., the most robust wave driver, using SPH (Smoothed Particle Hydrodynamics) and LES (Large Eddy Simulation). For the verification of numerical results, we also carried out hydraulic model test. It is shown that Eco-breaker 2 can effectively alleviate the reflection of long waves with its inherited large organized eddies encompassing the water chamber and some region off the curtain wall of varying size. It is also shown that the scope and strength of large organized eddies strongly depends on the incident wave period, and the reflection coefficient can be lowered to 0.18 by tuning the size of water chamber such that resident time at the chamber is just short of the half period of incident waves. Based on these results, we present the specification of Eco-breaker 2 to boost its use on the development of water environment friendly harbor worldwide.