Calculating true wind
I have a Simrad is20 wind transducer and display. The display is on the NMEA 2000 network, and is using the SOG and COG from the chartplotter, to calculate true wind.
Am I right in thinking that I really need a heading sensor to calculate true wind accurately?
I think that the calculation is assuming that the boat's heading is the same as the course, which is erroneous if there is a current at any angle to the heading.
So I think I need to use heading, and GPS SOG. Is this right?
Bristol 31.1, San Francisco Bay