DESIRED COURSE AND SPEED

Determine what course and speed you must use in order to make a desired course and a desired speed good with this information: desired course 265° , desired speed to be made good 15 knots, current set of 185° , and a drift of 3 knots.

Solution: From A draw line AB in the direction to be made good (265° ) and for a length equal to the speed to be made good (15 knots).

From A draw AC, the set and drift of the current, 185° and 3 knots.

Draw a line from C to B. The direction of this line is 276° ; this is the course to be steered. The length of the line equals the speed required (14.8 knots).

These current vectors can be made to any convenient scale and at any convenient place such as the center of the compass rose, unused area of the plotting sheet, a separate sheet of paper, or directly on the plot.

These current vectors can be made to any convenient scale and at any convenient place such as the center of the compass rose, unused area of the plotting sheet, a separate sheet of paper, or directly on the plot.

Leeway is the leeward motion of a vessel due to wind. It may be expressed as distance, speed, or angular difference between the course steered and the course made good through the water. The amount of leeway depends upon the speed and relative direction of the wind, type of vessel, exposed freeboard, trim, state of the sea, and depth of water. Leeway is most conveniently applied by adding its effect to that of the current and other elements introducing geographical error in the dead reckoning.