"b393capt" wrote in message
oups.com...
I am just about to buy a bunch of Raymaine instruments for my new B
393, and just found out that the ST60 is limited to using SOW, and
won't use GPS SOG & COG, to calculate true wind.

After looking thru this forum, I see some references to this issue, but
don't see either
(1) A way to get true wind on any of the Raymarine instruments, does it
work on the Tri data ??

(2) Another vendor who does not have this limitation mentioned.

Can anyone help me ?

Especially at low sailing speed and strong current, this can make all the
difference.
The Navman wind instrument can use either SOG or water speed for true wind
calculation.
You can also "fool" any NMEA wind instrument by converting the NMEA RMC
sentence from the GPS (COG) to VHW (speed thru water). A Brookhouse
multiplexer will do this for you. You can load a simple script for this
conversion. You may need a multiplexer anyway if you are building an
integrated instrument system.
Wout

"Wout B." wrote in message
...

"b393capt" wrote in message
oups.com...
I am just about to buy a bunch of Raymaine instruments for my new B
393, and just found out that the ST60 is limited to using SOW, and
won't use GPS SOG & COG, to calculate true wind.

After looking thru this forum, I see some references to this issue, but
don't see either
(1) A way to get true wind on any of the Raymarine instruments, does it
work on the Tri data ??

(2) Another vendor who does not have this limitation mentioned.

Can anyone help me ?

Especially at low sailing speed and strong current, this can make all the
difference.
The Navman wind instrument can use either SOG or water speed for true wind
calculation.
You can also "fool" any NMEA wind instrument by converting the NMEA RMC
sentence from the GPS (COG) to VHW (speed thru water). A Brookhouse
multiplexer will do this for you. You can load a simple script for this
conversion. You may need a multiplexer anyway if you are building an
integrated instrument system.
Wout


Sorry, I meant GPS (SOG) in my posting above, not GPS (COG).
Using SOG instead of speed thru water is useful if the paddle wheel of the
speed instrument gives a very inaccurate reading and/or is fouled. It is of
course only accurate if the heading of the vessel is the same as the COG, as
the measured wind-angle is relative to the centre line of the vessel.
Wout

You can also "fool" any NMEA wind instrument by converting the NMEA RMC

sentence from the GPS (COG) to VHW (speed thru water).

I checked out the web-site, this is very cool !!!

Does this work if my wind instrument is Raymarine's (does the ST60 use
sea talk ??)?

Dan

You can also "fool" any NMEA wind instrument by converting the NMEA RMC

sentence from the GPS (COG) to VHW (speed thru water).

I checked out the web-site, this is very cool !!!

Does this work if my wind instrument is Raymarine's (does the ST60 use
sea talk ??)?

Dan

Dan .
Raymarine has a converter available that converts SEA TALK to NMEA and
reverse, if you have a Raymarine Radar or chartplotter or FF ,RL/SL
series or newer, you can convert most of the data through the insrument
in lieu of any converter(external)
markvictor

Wout B. wrote:

Especially at low sailing speed and strong current, this can make all the
difference.
The Navman wind instrument can use either SOG or water speed for true wind
calculation.
You can also "fool" any NMEA wind instrument by converting the NMEA RMC
sentence from the GPS (COG) to VHW (speed thru water). A Brookhouse
multiplexer will do this for you. You can load a simple script for this
conversion. You may need a multiplexer anyway if you are building an
integrated instrument system.
Hi,

You can fool any NMEA wind instrument. But if you have a SeaTalk only
instrument, you have to "fool" the SeaTalk device.
If someone is interested in playing with it have a look at
www.tklinux.de

Frank

I think you are confusing true wind direction with magnetic wind
direction. To find true wind you need apparent wind (speed and
direction) from your masthead and boat speed from your paddle wheel.
To find magnetic wind speed/direction you need an instrument system
that accepts info from a fluxgate compass to do the calculations.
Signet SmartPak system for example.

I don't understand the reference to the paddlewheel rgnmstr. True wind
direction = wind direction (true north) if the boat was anchored at a
point on the water, e.g. not relative to the boats movement or water
current. To achieve this (with the boat in motion), you need the
apparent wind & speed, SOG (from the GPS) and ship heading (true north)
from your flux gate (COG from GPS introduces error) to get a close
approximation, and a little more accuracy can be had if you include
adjustments for angle of heel error, heading error (compensate for mast
& sail induced air flow), a yaw sensor on the mast, etc ... oh yea, and
you need an instrument package that uses this, some like Raymarine wont
use SOG from the GPS.

Interesting paper published that explains true wind, and notes that 80%
of marine vessels calculate it wrong.

http://www.coaps.fsu.edu/woce/truewind/paper/

Better squeeze up for the Brooks & Gatehouse...