TrueWind

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Revision as of 06:56, 31 October 2018 by Kannix (talk | contribs) (Wind)
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see also

Terms

vessel's Movement and Orientation

  • SOG Speed Over Ground navigation.speedOverGround
  • COG Course Over Ground (relative to true north) navigation.courseOverGroundTrue
  • COG Course Over Ground (relative to magnetic north) navigation.courseOverGroundMagnetic
  • STW Speed Trough Water navigation.speedThroughWater
  • HDG Heading
    • HDT Heading (relative to true north) navigation.headingTrue
    • HDM Heading (relative to magnetic north) navigation.headingMagnetic

Wind

  • AW Apparent Wind (relative to vessel)
    • AWS Apparent Wind Speed environment.wind.speedApparent
    • AWD Apparent Wind Direction (relative to true north) environment.wind.directionTrue
    • AWD Apparent Wind Direction (relative to magnetic north) environment.wind.directionMagnetic
    • AWA Apparent Wind Angle (relative to HDG) environment.wind.angleApparent
  • TW True Wind (relative to surface of the water)
    • TWS True Wind Speed (relative to water) environment.wind.speedTrue
    • TWD True Wind Direction (relative to true north) ???
    • TWA True Wind Angle (relative to HDG) environment.wind.angleTrueWater
  • GW Ground Wind (relative to ground) used in weather forecasts and reports
    • GWS Ground Wind Speed (relative to ground) environment.wind.speedOverGround
    • GWD Ground Wind Direction (relative to true north) ???
    • GWA Ground Wind Angle (relative to HDG) environment.wind.angleTrueGround

Current

  • DFT Current Drift (speed relative to ground) environment.current.drift
  • SET Current Set (direction relative to true north) environment.current.setTrue
  • SET Current Set (direction relative to magnetic north) environment.current.setMagnetic

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 = OGx - AWx = SOG * Sin (COG) - AWS * Sin (AWD)
    • TWy = OGy - AWy = SOG * Cos (COG) - AWS * Cos (AWD)
    • TWS= SQRT (TWx*TWx + TWy*TWy)
    • TWD True Wind Direction (relative to true north) ???
    • TWD = ATAN ( TWx / TWy )
  • S Speed over ground in direction of H
    • DFT Drift (speed relative to ground) ???
    • DFTx = OGx - SHx = SOG * Sin (COG) - S * Sin (H)
    • DFTy = OGy - SHy = SOG * Cos (COG) - S * Cos (H)
    • DFT= SQRT (DFTx*DFTx + DFTy*DFTy)
    • SET Set (direction relative to true north) ???
    • SET = ATAN ( DFTx / DFTy )

Wind 1.jpg

signalk-derived-data (assuming COG=H)

  • https://github.com/SignalK/signalk-derived-data/blob/master/calcs/groundWind.js
  • 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
    • TWA = ATAN2(AWy, -SOG + AWx)
    • TWS True Wind Speed (relative to ground) environment.wind.speedOverGround
    • TWS = SQRT (POWER(AWy,2) POWER(-SOG + AWx,2))

Wind 2.jpg

Sensors

Heading

SOG and COG

  • GPS receiver

STW

AWS and AWA