🔍 Key Concepts
• Meaning of each part of group Nddff on WS Form B-80 (N = total cloud cover in oktas, dd = true wind direction in tens of degrees, ff = true wind speed in knots).
• Difference between apparent wind and true wind, and how to use a velocity triangle with ship’s course and speed to convert between them.
• How cloud cover in fractions of the sky converts to oktas (eighths of the sky) for the N digit.
💭 Think About
• From 0three-quarters of the sky, what number of oktas does that correspond to, and which answer choices match that N value?
• How do you combine a course of 020T and a ship speed of 8 knots with an apparent wind of 17.7 knots from 226 relative to find the true wind vector (both direction and speed)?
• Once you have the true wind direction in degrees true, how do you convert it into the two-digit dd code, and how should you round the true wind speed to get ff?.
✅ Before You Answer
• Confirm that N is coded in eighths (oktas) of sky cover, not in simple fractions, and that 3/4 of the sky is converted correctly.
• Verify that you are using true wind, not apparent wind, in the Nddff group; apparent wind must be corrected for ships motion (both direction and speed).
• Double-check that dd is the true wind direction from which the wind is blowing, expressed in tens of degrees (00 36), and that ff is the true wind speed in whole knots, rounded according to the VOS coding instructions.