Working out a course to steer across the tide 1.

There are several variations on how you work out the correct course to steer when crossing the tide.

Which one you choose depends upon the situation and what you wish to achieve. Over the next few weeks I will look at the advantages and disadvantages of some of them.

Using a waypoint in the GPS receiver.

Most people use GPS as their main source of navigational information, so we will look at it first. However, it should be remembered that it might not be available all the time!

When you enter a waypoint in to your GPS, the bearing and distance to the waypoint are displayed.

To reach that waypoint, all you need to do is to turn on the the indicated bearing, then adjust the vessel's heading until the course over the ground function matches the bearing to the waypoint.

If the distance to go is set to read to 2 decimal places you can get very close to the waypoint, even if you can not see it (fog or an unlit buoy). If the waypoint is at a buoy, care must be taken that you do not run it down .

The cross track error should be at a minimum with this approach, so this function of GPS can also provide useful information.

Advantages	Disadvantages
This technique is very simple, and only requires a little practice to perfect.	Any technique should be practised before it is really needed. Stay below, with the curtains closed and navigate your way around a few courses!
It works best over relatively short distances.	This is not an efficient method over long distances, especially over several hours, when the tidal stream will change direction.
It is very accurate.	You must ensure the waypoint data is entered correctly.
You can be very confident in your position in fog.	You are relying on electronics, they may fail when you really need them.

Conclusion:

A very good technique for short passages when in confined waters, in any conditions of visibility, especially fog.

 

 

Sailtrain.co.uk is free to use, but if you feel you would like to contribute to the running and development costs you can donate via Paypal: