A Running Fix A Definition & How to plot on a chart What is a Running Fix? • A “fix” is a common term used when the vessel’s position can be confirmed by the intersection of two or more position lines i.e “fixing” the vessel’s position or, obtaining a “fix” • Position lines can be from celestial observations, terrestrial bearings, terrestrial ranges, GPS co-ordinates, etc • A running fix is when we combine two position lines, which are obtained at different times in order to obtain a fix • To so we must also know the ship’s course & speed Question 1, Paper • At 0930hrs in DR Lat 510 22’N, Long 0060 10’W an observation of the sun gave a bearing of 0820(T) and an Intercept of 0.8’ T • The vessel is steering 3100 (T) at a speed of knots • At 1200hrs a Meridian Altitude of the Sun gave a Latitude of 510 37’N • Find the vessel’s position at 1200 and also at 0930 Procedure • Plot the given DR position • Plot the given bearing, lay off the given Intercept and then plot the position line • Plot the vessel’s course from the ITP position • Using the ship’s speed, calculate the distance run during the time interval given (This calculation MUST be shown on your answer book) • Lay off the distance run on the plotted course • This will give the DR position for the time of the second observation • It is also the position through which we will transfer the first position line Procedure • Plot the first P/L through the second DR position This will be a “transferred” P/L • Plot the second P/L or Latitude (whichever is given) s • Where the two P/L’ intersect this will be the “fix” 1200 DR 1200 DR 0930 Procedure • Find the vessel’s postion at 0930 as follows • To the fix at 1200hrs, lay of the vessels course and distance steamed in the 2.5 hrs • This will give the position through which to transfer the observed noon latitude • Where the transferred noon latitude intersects with the morning position line will give the vessel’s position for 0930 1200 DR 1200 0930 DR 0930