"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

"Timothy.Rulon" wrote in message
...
b393capt wrote:
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 ?


To calculate true wind you also need true heading. SOW, SOG and COG
alone won't work as set/drift begin to effect your vessel which will
occur as you slow down. At zero speed, a GPS is likely to report
anything for COG unless it has a built in aid like a magnetic flux gate
compass. There are some expensive GPS receivers which provide true
heading by using 2 antennas and lower cost LORAN-C sensor units being
developed which does something similar. Should also work great as an
input to an autopilot rather than magnetic sensors which can get tricked
by magnetic anomolies.

I'm not aware of a recreation-priced system which performs all the above
but would very much like to hear about it for a government application.

For marine weather information, please visit
http://www.nws.noaa.gov/om/marine/home.htm

This is correct of course, but what is often referred to as "true" wind on a
sailboat as opposed to apparent, is relative to the centre line of the boat,
but corrected for speed. The T on the ST60 instrument actually stands for
"theoretical". Many nav software packages calculate the true wind direction
and speed from heading, relative wind angle, taking into account SOG and
COG, to plot a wind vector or lay lines in the chart.
Wout

On Thu, 8 Dec 2005 10:55:01 +1300, "Wout B."
wrote:


"Timothy.Rulon" wrote in message
...
b393capt wrote:
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 ?


To calculate true wind you also need true heading. SOW, SOG and COG
alone won't work as set/drift begin to effect your vessel which will
occur as you slow down. At zero speed, a GPS is likely to report
anything for COG unless it has a built in aid like a magnetic flux gate
compass. There are some expensive GPS receivers which provide true
heading by using 2 antennas and lower cost LORAN-C sensor units being
developed which does something similar. Should also work great as an
input to an autopilot rather than magnetic sensors which can get tricked
by magnetic anomolies.

I'm not aware of a recreation-priced system which performs all the above
but would very much like to hear about it for a government application.

For marine weather information, please visit
http://www.nws.noaa.gov/om/marine/home.htm

This is correct of course, but what is often referred to as "true" wind on a
sailboat as opposed to apparent, is relative to the centre line of the boat,
but corrected for speed. The T on the ST60 instrument actually stands for
"theoretical". Many nav software packages calculate the true wind direction
and speed from heading, relative wind angle, taking into account SOG and
COG, to plot a wind vector or lay lines in the chart.
Wout

And I thought the T in ST60 actually stood for 'Talk', part of
'SeaTalk', RayMarine's proprietary data flow protocol!

"Bil" wrote in message
...
On Thu, 8 Dec 2005 10:55:01 +1300, "Wout B."
wrote:


"Timothy.Rulon" wrote in message
...
b393capt wrote:
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 ?


To calculate true wind you also need true heading. SOW, SOG and COG
alone won't work as set/drift begin to effect your vessel which will
occur as you slow down. At zero speed, a GPS is likely to report
anything for COG unless it has a built in aid like a magnetic flux gate
compass. There are some expensive GPS receivers which provide true
heading by using 2 antennas and lower cost LORAN-C sensor units being
developed which does something similar. Should also work great as an
input to an autopilot rather than magnetic sensors which can get
tricked
by magnetic anomolies.

I'm not aware of a recreation-priced system which performs all the
above
but would very much like to hear about it for a government application.

For marine weather information, please visit
http://www.nws.noaa.gov/om/marine/home.htm

This is correct of course, but what is often referred to as "true" wind
on a
sailboat as opposed to apparent, is relative to the centre line of the
boat,
but corrected for speed. The T on the ST60 instrument actually stands for
"theoretical". Many nav software packages calculate the true wind
direction
and speed from heading, relative wind angle, taking into account SOG and
COG, to plot a wind vector or lay lines in the chart.
Wout

And I thought the T in ST60 actually stood for 'Talk', part of
'SeaTalk', RayMarine's proprietary data flow protocol!

Haha,
You're right!
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.