Difference between revisions of "TrueWind"

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(AWS and AWA)
(calculate True Wind from Apparent Wind)
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** <b>SET</b> Current Set (direction relative to true north) <b>environment.current.setTrue</b>
 
** <b>SET</b> Current Set (direction relative to true north) <b>environment.current.setTrue</b>
 
** <code>SET = ATAN ( DFTx / DFTy )</code>
 
** <code>SET = ATAN ( DFTx / DFTy )</code>
 +
http://2.bp.blogspot.com/-5xrObeSQIUI/UXWPPH_BzrI/AAAAAAAABTI/DOQB0TQ_69Y/s1600/True+True+Wind.jpg
  
 
== simplified, assuming H=COG ==
 
== simplified, assuming H=COG ==

Revision as of 09:41, 30 October 2018

calculate True Wind from Apparent Wind

  • AWA Apparent Wind Angle (relative to H) environment.wind.angleApparent
  • H Heading (relative to true north) navigation.headingTrue
    • AWD Apparent Wind Direction (relative to true north) environment.wind.directionTrue
    • AWD = MOD(H+AWA;360)
  • AWS Apparent Wind Speed environment.wind.speedApparent
  • COG Course Over Ground navigation.courseOverGroundTrue
  • SOG Speed Over Ground navigation.speedOverGround
    • TWS True Wind Speed (relative to ground) environment.wind.speedOverGround
    • TWx = SOG * Sin (COG) - AWS * Sin (AWD)
    • TWy = SOG * Cos (COG) - AWS * Cos (AWD)
    • TWS= SQRT (TWx*TWx + TWy*TWy)
    • TWD True Wind Direction (relative to true north) ???
    • TWD = ATAN ( TWx / TWy )
  • STW Speed Trough Water navigation.speedThroughWater
    • DFT Current Drift (speed relative to ground) environment.current.drift
    • DFTx = SOG * Sin (COG) - STW * Sin (H)
    • DFTy = SOG * Cos (COG) - STW * Cos (H)
    • DFT= SQRT (DFTx*DFTx + DFTy*DFTy)
    • SET Current Set (direction relative to true north) environment.current.setTrue
    • SET = ATAN ( DFTx / DFTy )

True+True+Wind.jpg

simplified, assuming H=COG

  • COG Course Over Ground navigation.courseOverGroundTrue
  • SOG Speed Over Ground navigation.speedOverGround
  • AWA Apparent Wind Angle (relative to H) environment.wind.angleApparent
  • AWS Apparent Wind Speed environment.wind.speedApparent
    • AWx = AWS * Cos (AWA)
    • AWy = AWS * Sin (AWA)
    • TWA True Wind Angle (relative to H) environment.wind.angleTrueGround
    • ATAN2(AWy, -SOG + AWx)
    • TWS True Wind Speed (relative to ground) environment.wind.speedOverGround
    • SQRT (POWER(AWy,2) POWER(-SOG + AWx,2))

see also

Sensors

Heading

SOG and COG

  • GPS receiver

STW

AWS and AWA