🧭 Sextant Horizontal Angles: Three-Landmark Fix, Error Growth and Danger Angle (2D chart)

A chart with three landmarks, a ship moving along the coast and an offshore rock. Two horizontal sextant angles give circles of position whose crossing is the fix; random sextant error scatters the fix, and a danger angle keeps the ship clear of the rock. Set distance offshore, reading error and landmark spacing, with five numerical checks.