True Wind Measurement

[bewitched]

Originally Posted by Ex-Calif

The angle is always referenced as magnetic..

Nahh - that's the direction - the angle is relative to the boat (TWA, AWA)

[noelex 77]

On a cruising yacht I find true wind speed and direction one of the more useful displays that can be shown on my multitude of electronic gadgets.
The Raymarine will only calculate "true wind" from the log, there is no option to calculate it from the GPS.

[GordMay]

Do you have the manual?
Here ➥ http://www.raymarine.com/raymarine/S...81105_4www.pdf
or
Here ➥ http://www.cncphotoalbum.com/serviceguides/st60wind.pdf

[richardhula]

[JayH]

The Raymarine ST60 wind instrument will only calculate TWS from the log. It will not use SOG from the GPS, even if it is available on the network.

I use the device below to convert the SOG from the GPS into a SeaTalk "speed through water" sentence that the wind instuments will use. Look at the documentation and see configuration setting #14. This way my instruments display TWS with no log or paddlewheel in the water. It works great.

SeaTalk NMEA Bridge & Repeater

[Ex-Calif]

Originally Posted by bewitched

Nahh - that's the direction - the angle is relative to the boat (TWA, AWA)

Uhh. Sure. Measured by a magnetic compass, right?

Unless you mean the TWA is +30, -30, whatever degrees off 0. Then I understand.

[Troubadour52993]

The ST60 only gets boat speed info from the speed paddlewheel if you have a triducer in the water. If the paddlewheel is out, or you don't have a triducer, the ST60 will read true and apparent as the same.

FWIW, I did the "calibration" to try and make the SPEED match SOG from the GPS, but it's still off a bit, especially when speed is a few knots different from where I set the "calibration constant". At least to my knowledge, there is no way to get the ST60 wind to use the GPS SOG on seatalk as the boat speed input. I wish there were, as I trust it more than SPEED. Ditto for Trip Log.

[noelex 77]

Originally Posted by Troubadour52993

The ST60 only gets boat speed info from the speed paddlewheel if you have a triducer in the water. If the paddlewheel is out, or you don't have a triducer, the ST60 will read true and apparent as the same.

FWIW, I did the "calibration" to try and make the SPEED match SOG from the GPS, but it's still off a bit, especially when speed is a few knots different from where I set the "calibration constant". At least to my knowledge, there is no way to get the ST60 wind to use the GPS SOG on seatalk as the boat speed input. I wish there were, as I trust it more than SPEED. Ditto for Trip Log.

This is a problem with the ST60 series. At this price point they should allow the option of input of SOG from the GPS. It would be a simple software update.
There is some debate about which is the most useful "true wind" derived from SOG or STW. I feel SOG is more useful for cruising yachts, but others disagree.
For "true wind" derived from STW the log needs to be accurate which in my experience is not found on cruising boats. The true wind varies, even in non tidal waters, with the tack and point of sail, making the data useless.
Try the same with "true wind" derived from SOG via the GPS and the data is rock solid and accurate.
"True wind is very useful, but if you have to make allowances for port and starboard tack or how many days since you last cleaned the paddlewheel the information is meaningless. Get a system that uses the GPS input and you will learn the value of accurate "true wind"

[Bash]

Originally Posted by Ex-Calif

Unless you mean the TWA is +30, -30, whatever degrees off 0. Then I understand.

I've always understood it to be that way. TWA is a relative bearing, while TWD (direction) is a compass bearing.

much simpler in the log book: wind 15 kts T at 160°

[GordMay]

True & Apparent Wind Calculation Formulas & explanations, & Online Calculators

➥ True and Apparent Wind Calculator