peaman
Sustaining Member
"True wind" is what you would see if you were not moving. Everyone close by should see the same true wind. But your wind instrument sees the wind to be "apparently" more if your boat is moving into the wind, than another boat will when heading in the opposite direction. In order to calculate "true" from a reading of "apparent" wind, you need to make a vector math correction for your boat speed relative to earth.According to all the "experts" SPW is the source you need to get true wind info.
Note too, that your sails only care about apparent wind.