Dead Reckoning (DR) and Estimated Position (EP)

Dead Reckoning (DR) is the process of estimating your position based solely on your course steered and distance run through the water — without accounting for tidal stream or leeway. It gives a basic 'where we should be' position.

An Estimated Position (EP) builds on DR by adding estimated tidal stream and leeway. It is a fuller estimate, not a guarantee of accuracy: poor inputs can make it wrong. On the chart, mark a DR with a cross and 'DR', and an EP with a triangle and time.

At Yachtmaster level you are expected to chain DR and EP across multiple hours — for example, advancing an EP from hour one and applying a new tidal stream vector for hour two. Each successive EP carries forward the accumulated error, so taking a fresh fix whenever possible is critical.