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ground wind

The vector difference between the apparent wind (AWS, AWD) and the vessel motion through the water (STW, CTW) is called the true wind. This is the wind relative to the water. This is the wind that is used in polar diagrams to evaluate sailing performance.

The vector difference between (AWS, AWD) and (SOG, COG) is called ground wind. This is the wind relative to the fixed earth. This is the wind that meteorologists talk about and this is the wind given in forecasts and in model output, such as GFS winds at 10m.

If there is no current affecting the vessel, SOG=STW and COG=CTW, so these winds are the same. This distinction only matters for sailboat navigation analysis and tactics in areas with notable current.

See True wind and ground wind and why we need both which includes a link to a related background article.

See true wind


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