The methods of celestial navigation to fix the ship position in line with the stars are only applied in the twilight time interval when both the celestial bodies and the horizon apppear simultaneously. This means that these methods cannot be used during the night even if the stars are visible. This paper proposes a novel approach which uses the azimuth of the celestial body in order to establish the great circle equation relating the observed body to the ship position when the celestial bodies appear. In addition, the proposed method does not demand the horizon and sextant equipment as with the previous methods. The key advantage which differentiates this method from previous ones is its ability to determine the ship position during the night when the horizon is invisible. Firstly, the vector calculus is applied to find the mathematical equation for the ship position through analyzing the relationship between the ship position and the great-circle azimuth of the observed body. Secondly, the equation system for the ship position is expanded into a standard system in which the input for the proposed mathematical system are the great-circle azimuth and the coordinates of the observed body. Finally, the numerical technique is also proposed to solve the nonlinear system for the ship position. To verify the validation of this proposed method, a numerical experiment is carried out and the results show that it can be applied well in practice.

The computer can be used to display a continuously updated list or plot of vessel position. The computer that accept input data from a number of different navigation systems, e.g., Loran , Satnav, Radar, Decca, Compass, Sextant with electrical output etc., can compute the position of a vessel relative to prerecorded objects. The celestial navigation system requires the computer to do not much calculation. Calculation are for trigonometeric, linear systems, finding roots of nonlinear equation and least square estimation etc, . In order to computerize the celestrial navigation system, these calculations must be programmed. The purpose of this thesis is to study the formulation, the design and the test of calculations of the coordinates of celestial bodies, the altitude correction and the solution of the navigational triangle processes.