Three-Point Bearing

A three-point bearing fix, also called a three-point angle fix or horizontal sextant angle fix, is obtained by measuring the horizontal angles between three charted objects simultaneously using a sextant held horizontally. The two angles—between the left and centre object, and between the centre and right object—are then plotted using station pointer circles or a tracing paper overlay to find the unique point on the chart from which those angles would be observed. Bowditch (American Practical Navigator) covers the technique and the mathematical alternatives using trigonometric formulas. This method is highly accurate and immune to compass error, making it valuable in areas where compass deviation is large or uncertain. It requires clear visibility of three well-separated charted objects and a sextant in serviceable condition. In practice, the technique is less commonly used than radar or ECDIS fixes because of the time required for plotting, but it remains an important contingency skill for the OOW and is examined under STCW. Celestial navigators adapt the same principle to the star sight, replacing horizontal angles with measured altitudes and using sight reduction tables to derive position lines.