While installing a wind sensor on my boat using Signal K (which is awesome BTW!), I was frustrated to find I couldn't get it to calculate true wind without a knotmeter because it requires speed through the water (STW). I was able to jump through hoops and make STW mirror GPS speed over ground, and along the way I found someone already created a GitHub feature request to make this easy, but it was rejected because it's "wrong." Why? I can't see any reason to use STW except as a relic of the days before GPS.
Where I sail, tidal currents are a thing, so STW is a pretty terrible indicator of how fast - or in which direction - my boat is actually moving. Not to mention the paddle wheel is always getting fouled and is only accurate at the start of the season (if it works at all). "True" wind, thus calculated, therefore tells me how fast the wind is moving relative to the tide. I actually need "ground wind" if I want to know how hard the wind is actually blowing, or from which direction, although unlike "true" wind it's relative to the compass, not the bow. Since the tide has no bearing on my sails, I fail to see why it should factor into windspeed calculation.
So...is there a purpose / value of "true" wind that I'm missing, or is it indeed just a relic? I feel like apparent and "ground" wind are the only things I should care about.
Where I sail, tidal currents are a thing, so STW is a pretty terrible indicator of how fast - or in which direction - my boat is actually moving. Not to mention the paddle wheel is always getting fouled and is only accurate at the start of the season (if it works at all). "True" wind, thus calculated, therefore tells me how fast the wind is moving relative to the tide. I actually need "ground wind" if I want to know how hard the wind is actually blowing, or from which direction, although unlike "true" wind it's relative to the compass, not the bow. Since the tide has no bearing on my sails, I fail to see why it should factor into windspeed calculation.
So...is there a purpose / value of "true" wind that I'm missing, or is it indeed just a relic? I feel like apparent and "ground" wind are the only things I should care about.
Here we go .... 
