LT Chuck Williams

1
Correcting Wind Speeds for vessel movement

• By
• LT Chuck Williams

Note All Decimal Days are for 21 July, 2006.
2
Brief Outline

• Position
• Variability
• UDAS COG
• UDAS SOG
• How are True Winds calculated?
• Heading input from GPS vs. True Winds
• Results / Conclusions
• Further Studies

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GPS Position(s)
4
Variability
5
Where does UDAS get COG ?
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How accurate is UDAS Course?
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How accurate is UDAS Speed (kts)?
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Heading vs. True Wind
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Results / Conclusions

• Positions for all instruments were fairly
  accurate
• When measured directly from GPS
• There are always variations in Ships Speed
• These variations increase dramatically at low
  speeds
• There are always variations in Ships Course
• These variations increase dramatically at low
  speeds
• There are minimal variations in the heading
• When measured directly from UDAS
• Speed (applying various filters and running means
  to raw GPS data) was always lower than the Raw
  data.
• Difference was lt 1 kt ? minimal impact
• Seems to use a 60 second running mean, then
  extracts every 36th Second.
• 36 seconds is the time to complete one loop of
  data collection
• UDAS COG Follows True Course
• GPS Heading and UDAS Gyro very similar

10
Further Studies

• If study is repeated
• Have ship do ONE or more circles
• Have someone look into the MatLab Signal Browser
• Can more correctly remove ships movement (pitch
  / roll)
• Etc