Pre-Plotted fix.

Due to the lack of time that can be spent below decks working on the chart when in pilotage waters, the conventional fix plotting approaches can take too long. In addition to this, if a fix is taken and a position placed on the chart, this position immediately becomes inaccurate as the boat moves away.

Pre-Plotted Fixes

A means of dealing with this situation is to pre-plot fixes on the chart and then manoeuvre the boat to those positions. A good example of this occurs when approaching an anchorage at night.

If the desired anchoring position is placed on the chart and two bearings drawn through that point, all the navigator need only follow one of the bearings until the second one is reached.

Pre-Plotted Fix.

Of course, this is not as simple as that. The vessel must be kept on the course that ensures that the bearing to the first light remains correct. Because of this it is usually easier to use the approach that is most parallel to the direction of the tidal stream.

Once the light has been clearly identified, lining up the light with the background creates a transit. This means that instead of constantly checking the bearing with the compass, the helmsman just needs to keep the light in line with a feature on the shore.

This technique is easiest if the lights are ahead of the vessel, but there is no reason why they should not be astern, it is just harder for the helmsman to stay on the line. You will also find that coloured lights are easier to track than white ones (they blend it to the streetlights), and it is best to choose lights with long periods of illumination.

As well as being useful when anchoring, this technique is useful for either finding or avoiding unlit marks at night. When entering an unlit harbour, the buoys can be found by the cautious application of this approach, or at night, unlit racing and steel mooring buoys can be avoided; just make sure you are not where the bearings cross!

Pre-Plotted Grids

In a situation where the vessel is passing through a large area that has numerous hazards a grid of bearings can be plotted on the chart. Because the lines will intersect, the approximate position of the boat can be found very rapidly.

Pre-Plotted Grid of Bearings.

Obviously when this is prepared, the bearing of each line should be marked by that line.

This approach will not tell you where you are, but you will know which segment of the chart the vessel is in and approximately how long it will remain in safe water.

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