Dead Reckoning (DR) and Estimated Position (EP)

Start a dead-reckoning plot from a known or accepted position. Advance the vessel using the course or track through the water and the distance run through the water. In the Day Skipper convention used here, the DR excludes tidal stream and leeway so those assumptions remain visible rather than being hidden inside the first line.

An estimated position applies the best available estimates of leeway and tidal stream to the DR construction. Because the current, wind effect, steering and log may all differ from the values used, an EP is a reasoned estimate rather than a fix. It may be more useful than the uncorrected DR, but it is not automatically more accurate than every other position source.

Label the time and use the notation required by the course material. In the plotting convention used in this product, a DR is shown with a cross and an EP with a triangle containing a dot. The label is valuable only when the inputs and uncertainty are also understood. Near danger, shorten the interval between checks and seek fresh position evidence.