Projected EP – DS & YM


Before reading this page you will need to have a copy of the training almanac and chart (and a real ones if possible).

You will need to be happy calculating Estimated Position before reading this page.

Why is this important?

If you are in a motor boat and can point your boat in just about every direction you can calculate a Course to Steer (CTS) and point your boat in the desired direction.

If you are in a sailing boat and you are sailing up wind you cannot always use a CTS as the direction you need to go is up wind. Projected EP allows you to calculate your estimated position in the future if you continue on the present heading.

The information we need

You will need to know the direction you will be travelling for a period of time (say an hour), the amount of leeway, the speed you are likely to travel at and the tidal current that will act on you over that time.

The best way to illustrate the next steps is with an example. So lets assume at 10:00 we are positioned in 46o 23.1’N 006o 22.4’W.

With a easterly wind the best course to windward is 045oM at 5kt. We want to know where we will end up after one hour.

The tide for the next hour will flow in the direction 322o(T) at 1.3kt. We will allow 5o for Leeway.

Plotting our Predicted EP

We start by plotting our position, this could be by a number of methods ie.GPS, Traditional Fix or EP. The method of plotting is then identical to a normal EP.

To see the whole method explained watch this video.

Video: skill

Calculating the tidal stream

In a real life situation you will not be simply given the tide speed and direction but will need to calculate it using the method shown on the tidal stream webpage.


Keep practising this method and make sure you know the difference between this, EP and CTS.


The content of these pages is put together in good faith and is constantly evolving. It is possible that errors exist within this content. If you spot an error or would like to add anything to these pages please contact use via email.

Reading the content of these pages is not a substitute for completing a RYA Shorebased course or similar.