Running fix (how to plot on the charts)

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 o

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 do so we must also know the ship’s course & speed

Question 1, Paper 1

• 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 8 knots

• The vessel is steering 3100 (T) at a speed of 8 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

• 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.

• 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)

• Where the two P/L’s intersect this will be the “fix”

1200

1200

DR 0930

• 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

DR

1200

DR 0930

0930