I thought I'd start a new thread so that we don't take the wind speed topic (which is related to his Garmin instrument) too far off base. I've said that I use the GPS speed input for the true wind calculation. Thanks to @DrJudyB and the posted article (copied here) I have a better understanding why "boat movement thru water" or paddlewheel input is best. However, it seems to me that it is best simply because it best represents your targets with respect to the polars. Throw the polars out and what difference does it make? Of course that is heresy to racers. But the objective is to maximize VMG, isn't it? I understand that the way to maximize your VMG is to hit the targets relative to boat speed through water and true wind angle.
Airmar CS4500 Part II (Reliable True Wind) - Panbo
Believe me, I'm not trying to be contrary. My understanding is that the goal of VMG is to maximize your speed over ground to the mark, which is set on ground and doesn't move with the current (unless it comes loose). If your true wind input is GPS, then don't you know that current is going to offset the "true wind" heading (true wind as defined in the article, not "ground wind") and distort the boat speed so that it doesn't match SOG. You wouldn't look for the same targets on both tacks. Instead you will set your targets based on the best VMG. It sounds backwards, and I'm sure that it's just making it over-complicated. But the article led me down this path. The last paragraph (written mainly for power boats) talks about the value of "ground speed" if you have a good heading source and your chartplotter can input current set and drift.
So, my B&G chartplotter has that capability with the external GPS sensor B&G ZG100 (with heading sensor) all integrated on NMEA 2000 network. Wouldn't it be feasible for the chartplotter and displays to calculate and display "True Wind" and "Boat Speed" from the inputs that include Apparent wind from the wind sensor, GPS boat speed, and current set and drift from the chartplotter/heading sensor. In that sense, you would not be dependent on a paddlewheel input and you can have your True Wind heading and boat speed displayed to achieve the targets in the polars.
Just askin'
Airmar CS4500 Part II (Reliable True Wind) - Panbo
Believe me, I'm not trying to be contrary. My understanding is that the goal of VMG is to maximize your speed over ground to the mark, which is set on ground and doesn't move with the current (unless it comes loose). If your true wind input is GPS, then don't you know that current is going to offset the "true wind" heading (true wind as defined in the article, not "ground wind") and distort the boat speed so that it doesn't match SOG. You wouldn't look for the same targets on both tacks. Instead you will set your targets based on the best VMG. It sounds backwards, and I'm sure that it's just making it over-complicated. But the article led me down this path. The last paragraph (written mainly for power boats) talks about the value of "ground speed" if you have a good heading source and your chartplotter can input current set and drift.
So, my B&G chartplotter has that capability with the external GPS sensor B&G ZG100 (with heading sensor) all integrated on NMEA 2000 network. Wouldn't it be feasible for the chartplotter and displays to calculate and display "True Wind" and "Boat Speed" from the inputs that include Apparent wind from the wind sensor, GPS boat speed, and current set and drift from the chartplotter/heading sensor. In that sense, you would not be dependent on a paddlewheel input and you can have your True Wind heading and boat speed displayed to achieve the targets in the polars.
Just askin'