A dead reckoning (DR) position is calculated by using the course steered and speed through the water as shown in Figure 11.1. We usually either over or underestimate our boat speed. Over a few hours an error of a fraction of a knot puts your position out by miles. If you steer a good course and get the tides and leeway right then you will be on track but ahead or behind your estimated position (EP). You still pick up your landfall, albeit either earlier or later than expected. It helps to have a log.
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