WIND 



25 



Figure 2.- -Determination of true wind from the apparent wind, using 

 Form 1209 and the associated ship's- speed scale. Given an apparent wind of 

 15 knots, 60° off the port bow, ship's speed 20 knots and heading 160°. Note 

 the use of the scale in locating point 2, which is always below point 1 (the 

 apparent wind) on a line through point 1 parallel to the vertical (green) lines 

 on the form. The upper figures at the end of the radial lines (used in deter- 

 mining the direction of point 1) represent direction from 0°-- 180° off the 

 bow (measured clockwise when off the starboard bow and counterclockwise 

 when off the port bow); the lower figures (in green) are used when determin- 

 ing the direction of point 2, which is measured clockwise from the bow. The 

 sum of the ship's heading and the direction of point 2 (226°) is 386°. Since 

 this sum exceeds 360, the true wind direction is 386-360 = 26°. 



