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) improves on DR by adding the effect of the tidal stream (set and drift) and an estimate of leeway (sideways drift caused by wind). The EP is more accurate than a DR position. On the chart, a DR position is marked with a cross and 'DR', an EP is marked with a triangle and the time.

At Coastal Skipper 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.