What data do I need to get True Wind with my Raymarine system?

[Steve - Raymarine - Moderator]

The algorithm to determine true wind is a marine industry standard and not just “Raymarine’s” way.

The above entry includes a link to a very good Ockam (http://www.ockam.com/docs/WhyPaddles.pdf ) article addressing True Wind calculation. Raymarine products require the following data items to calculate True Wind data:

• Apparent Wind (Wind instrument)

• Heading (Autopilot or Heading sensor)

• Speed Through Water (Speed instrument or speed transducer with a speed paddle wheel)

SJC FAQ#

[Dave]

Is there any way to configure any Raymarine instrument to used speed over ground instead of speed through the water as input for true wind speed/angle?

I have a paddle wheel speed transducer, but got tired of putting it in and taking it out each time I sail. It collects algae fairly quickly. I find speed over ground to be more useful anyway.

Your post indicated the algorithm is an industry standard, but it seems with the proliferation of GPS, reliance on speed through the water as the input might be a little dated. It seems to me that if a boat is moving with or against a current, an algorithm relying on water speed would skew the "true" wind speed and direction.

[Chuck - Raymarine - Moderator]

Dave,

This subject has been addressed many times before within this and other forums. It is not possible to do as you have suggested, as it would cause the reference frame for True Wind (sometimes called True Relative to Boat) to be changed from the boat's reference frame to the ground reference frame. Per Raymarine and other high performance manufacturers of racing instruments (see the article referenced within the prior response, True Wind requires speed through water and heading data.

[Dave]

Thanks, Chuck. I should have read the article first.

[Chuck - Raymarine - Moderator]

You're welcome.