HND Nautical Science
Running Fix with current & Leeway.
Running fix uses the ability to transfer position lines through a time interval and utilises the best fixing method available whether it be a Dead Reckoning (DR) or if current and wind (leeway) are supplied Estimated Position.
In applying a running fix to a chart the following outlines basic steps that must be taken to produce a position.
1. Bearings taken by Compass or Gyro must be corrected to true.
2. The initial and second position line laid off on the chart once corrected.
3. A position chosen on the initial position line to run off a DR or EP construction from.
4. From the chosen position lay off the corrected water track.
Corrected Water track : a) Corrected for Compass or Gyro Error then:-
b) Leeway applied downwind.
5. The water track will be for the same time interval as the interval between initial and second bearing.
6. Apply the current at the end of the above corrected water track the length of the current being for the appropriate time interval (initial to second P/L time interval)
7. At the end of the current this position will be the EP and joining the chosen position to the EP gives the Ground track, (CMG SMG course and speed made good)
8. Transfer the initial position line through the EP and where the transferred position line intersects the second position line is the final position.
9. The initial position can be found by laying back the ground track (i.e. line joining initial position to the EP) from the final position to where it intersects the initial position line.
DGR/AWS/09/06 Chartwork and Tides 1 of 1
dariusz.lipinski