ABSTRACT: This study proposes a simple method for obtaining a celestial fix, developed within a Geographic Information System (GIS) under the framework of an ECDIS system. The underlying principle is dependent on the most fundamental theory in celestial navigation; the circle of position (COP) of the celestial bodies is plotted to find the fix. Through the spatial data processing, analysis, and visualization capabilities available in GIS, a celestial fix may be obtained directly from plotting. This eliminates the limitations associated with finding the fix manually using a paper map, but also avoids the cumbersome work and inaccuracy of the traditional Intercept Method (IM) or the complicated, and often obscured, computation involved in numerical methods. The proposed method is simple and accurate, and it applies to problems involving two or more celestial bodies and high-altitude observations. It provides a reference for the development of a celestial positioning module in an ECDIS system, and could also be integrated into an educational program on electronic celestial navigation.

KEYWORDS: Geographic Information System (GIS), Celestial Fixing, Astronavigation, 1-2-3 Rule, Dead Reckoning (DR), Circle of Position (COP), Intercept Method (IM), Two-Body Fix

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