" RUNNING FIX "
A running fix can be obtained by using the mathematical relationships involved as shown above. A ship is steaming past lighthouse D. At point A, a bearing of D is observed and expressed as degrees right or left of the course (a relative bearing if the ship is on course). At a later time at point B, a second bearing is taken of D and expressed the same as before. At point C, the lighthouse is broad on the beam. The angles at A, B, and C are known, as are the distances between these points. Trigonometry can be used to find the distance from D at any bearing. Distance and bearing provide fix.
