true wind prompt: what is a true wind? how is the true wind defined in terms of the reference frame?...
DESCRIPTION
Suspect True Direction Data Facilitator Notes: When you see a signal of the motion of the ship in your “true” wind data, that should raise a red flag.TRANSCRIPT
![Page 1: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/1.jpg)
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True WindTrue Wind
![Page 2: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/2.jpg)
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Suspect True Direction DataSuspect True Direction Data
![Page 3: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/3.jpg)
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Suspect True Speed DataSuspect True Speed Data
![Page 4: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/4.jpg)
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Coordinate SystemsCoordinate Systems
![Page 5: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/5.jpg)
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DefinitionsDefinitions• True Wind (T) – Wind vector with
• speed and direction referenced to fixed Earth and• direction from which the wind blows referenced to true north (not
magnetic north).
• Apparent Wind (A) – Wind vector with• speed referenced to the vessel and• direction from which the wind blows referenced to true north.
• Platform-Relative Wind (P) – Wind vector with • speed and direction referenced to the vessel and• direction from which the wind blows referenced to the bow.
![Page 6: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/6.jpg)
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DefinitionsDefinitions• Course Over Ground (C)
• Vector motion of the vessel with a speed and direction to which the vessel is traveling referenced to true north.
• Heading (hθ) • The direction to which the
bow of the vessel is pointing referenced to true north.
![Page 7: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/7.jpg)
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DefinitionsDefinitions
• Zero-line-reference (Rθ) • The angle between the zero
line on the wind vane (anemometer) and the bow of the vessel;
• Measured clockwise from the bow.
![Page 8: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/8.jpg)
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Impact of 180˚ Error in RImpact of 180˚ Error in Rθθ
![Page 9: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/9.jpg)
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1D Example of True Wind Vector Math1D Example of True Wind Vector Math
• Vessel stationary on day with true wind is blowing directly over the bow.
![Page 10: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/10.jpg)
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1D Example of True Wind Vector Math1D Example of True Wind Vector Math
• Vessel moves forward inducing additional wind relative to the vessel.
![Page 11: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/11.jpg)
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1D Example of True Wind Vector Math1D Example of True Wind Vector Math
• T = A – M
• M = –C
• T = A – (–C) = A + C
![Page 12: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/12.jpg)
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Calculation DetailsCalculation Details
1. Calculate the apparent wind in math coordinates.A’θ = 270˚ – (hθ+Rθ+Pθ)
|A| = |P|
1. Adjust the course over ground to math coordinates.C’θ = 90˚ – Cθ
![Page 13: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/13.jpg)
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Calculation DetailsCalculation Details3. Calculate the components of the true wind vector.
Tu = T’u = |A| cos(A’ θ) + |C| cos(C’ θ)
Tv = T’v = |A| sin(A’ θ) + |C| sin(C’ θ)
• Calculate the true wind speed and direction from which wind is blowing.|T| = (Tu
2 + Tv2)0.5
T θ = 270˚ – arctan(Tv/Tu)
• Arctan function must have a range of -180˚ to +180˚.
![Page 14: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/14.jpg)
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Averaging ErrorsAveraging Errors
![Page 15: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/15.jpg)
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Turning Ship Alters Apparent WindTurning Ship Alters Apparent Wind
![Page 16: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/16.jpg)
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Incorrect Averaging MethodIncorrect Averaging MethodCourse Speed Heading P. Wind
DirectionP. Wind Speed
True Wind Direction
True Wind Speed
0.0 5.0 0.0 300.0 10.0
350.0 5.0 350.0 305.0 10.5
340.0 5.0 340.0 310.0 11.0
330.0 5.0 330.0 315.0 11.5
320.0 5.0 320.0 320.0 12.0
310.0 5.0 310.0 330.0 13.0
300.0 5.0 300.0 340.0 13.5
290.0 5.0 290.0 350.0 14.0
280.0 5.0 280.0 355.0 14.5
270.0 5.0 270.0 0.0 15.0
315.0 4.4 315.0 331.2 11.7 271.1 8.1
![Page 17: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/17.jpg)
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Correct Averaging MethodCorrect Averaging MethodCourse Speed Heading P. Wind
DirP. Wind Speed
True Wind Dir
True Wind Speed
0.0 5.0 0.0 300.0 10.0 270.0 8.7
350.0 5.0 350.0 305.0 10.5 266.8 8.7
340.0 5.0 340.0 310.0 11.0 263.8 8.7
330.0 5.0 330.0 315.0 11.5 261.1 8.7
320.0 5.0 320.0 320.0 12.0 258.5 8.8
310.0 5.0 310.0 330.0 13.0 263.9 9.0
300.0 5.0 300.0 340.0 13.5 269.0 9.0
290.0 5.0 290.0 350.0 14.0 274.5 9.1
280.0 5.0 280.0 355.0 14.5 272.4 9.5
270.0 5.0 270.0 0.0 15.0 270.0 10.0
267.1 9.0
![Page 18: True Wind Prompt: What is a true wind? How is the true wind defined in terms of the reference frame? Answer – A true wind is a wind vector with magnitude](https://reader036.vdocuments.mx/reader036/viewer/2022062503/5a4d1ad17f8b9ab059971580/html5/thumbnails/18.jpg)
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Questions?Questions?