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Old 15-11-2013, 21:37   #16
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Re: terminology ........ whats your flavour ???

"Radio check" on channel 16.
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Old 15-11-2013, 21:40   #17
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Re: terminology ........ whats your flavour ???

TWD = True Wind Direction is an angle measured from North (usually magnetic north). It is not referenced to the ground or the water but to the earth's magnetic field. If I am standing on my boat, the boat is anchored in a clear area, the wind will be True Wind and the direction can be measured relative to Magnetic north. Usually wind direction is given using the cardinal system or azimuth degrees.
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Old 15-11-2013, 21:41   #18
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Re: terminology ........ whats your flavour ???

> "Radio check" on channel 16.

Can be useful if the monitoring station is monitoring multiple channels.
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Old 15-11-2013, 21:47   #19
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Re: terminology ........ whats your flavour ???

TWD (same local, same time) will also change with wind speed, ie: gusts, and altitude. It is still measured in magnetic degrees.
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Old 15-11-2013, 21:52   #20
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Re: terminology ........ whats your flavour ???

Rule of thumb for TWD: If it's written, it's True - if it's spoken, it's magnetic

METAR v ATIS for example
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Old 15-11-2013, 22:06   #21
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Re: terminology ........ whats your flavour ???

Quote:
Rule of thumb for TWD: If it's written, it's True - if it's spoken, it's magnetic

METAR v ATIS for example
I did not know that. Interesting. I don't recall that difference from my pilot training.
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Old 15-11-2013, 22:34   #22
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Re: terminology ........ whats your flavour ???

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TWD = True Wind Direction is an angle measured from North (usually magnetic north). It is not referenced to the ground [...] but to the earth's magnetic field.
Wow, that's a fine distinction! For what it's worth, NOAA weather reports and forecasts (WFAX and GRIB) use a True North reference.
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Old 15-11-2013, 22:37   #23
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Re: terminology ........ whats your flavour ???

More of a pet peeve, but when people on the radio say "break" and wait a few seconds while still pressing the push-to-talk button! You're supposed to be listening when you break! There is a USCG radio operator in the Northern California area that always does this. Didn't she learn anything about radio operation???
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Old 15-11-2013, 23:13   #24
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Re: terminology ........ whats your flavour ???

Right of way still has some usage, strictly among sailboat racers while racing.
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Old 16-11-2013, 01:52   #25
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Re: terminology ........ whats your flavour ???

When sailing "true wind" is referenced to the water. This came about because before satellite navigation systems is was impossible to reference wind to land.

When this became possible "true wind referenced to the ground" needed a new term so became known as "ground wind"

Unfortunately we are stuck with very poor terms. Most sailors assume "true wind" must be referenced to the ground, after all that is what you would expect.

The other unfortunate consequence of this is many instrument systems will only display "true wind" for most cruising boats "ground wind" is more accurate and useful. It would be a very easy software adjustment for instrument manufacturers to at least make this option available so we could choose, but few do, probably because most consumers are under the mistaken belief that when their instruments are displaying "true wind" they are seeing what is more correctly called ground wind.
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Old 16-11-2013, 02:52   #26
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Re: terminology ........ whats your flavour ???

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And one knot is about 3,093.2 furlongs per fortnight.

Here are some terms that I thought were standard, but some were unfamiliar with them:

AWA = Apparent Wind Angle
AWS = Apparent Wind Speed
AWA and AWS are measured from your boat.

TWS = True Wind Speed
TWA = True Wind Angle
but referenced to what? Some say it's to the ground, and others say it's to the water. What would be your alternate terms and definitions?

TWD = True Wind Direction (I say this is referenced to the ground)
so... true wind, to you means water reference
but TWD is ground referenced is this what you are saying

true wind. to me means .... the direction and its velocity referenced to the ground ( TRUE NORTH) if you are plotting a CTS on a paper chart this is your point of reference, but it would appear we cannot then take this to the helm and use it to our electronic wind instruments...... ?
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Old 16-11-2013, 03:10   #27
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Re: terminology ........ whats your flavour ???

I hadn't really thought about the difference between Water and Ground referenced True Wind (the first place it was important to me was flying where it is Ground referenced).

I can see that before GPS it was difficult to determine ground based at sea unless you knew what the tide and currents were doing.
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Old 16-11-2013, 03:28   #28
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Re: terminology ........ whats your flavour ???

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so... true wind, to you means water reference
but TWD is ground referenced is this what you are saying

true wind. to me means .... the direction and its velocity referenced to the ground ( TRUE NORTH) if you are plotting a CTS on a paper chart this is your point of reference, but it would appear we cannot then take this to the helm and use it to our electronic wind instruments...... ?
Can someone explain to me ..

On an electronic wind instrument ( say a raymarine) you have a toggle to go from true to app, I understood this was the wind at the top of the mast (sender) with the angle and velocity of forward motion calculated to give you apparent wind , therefore true wind in this instance, is water referenced for velocity but magnetic north referenced for direction from your flux gate compass ?
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Old 16-11-2013, 03:35   #29
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Re: terminology ........ whats your flavour ???

[QUOTE=StuM;1392063]I hadn't really thought about the difference between Water and Ground referenced True Wind (the first place it was important to me was flying where it is Ground referenced).

I can see that before GPS it was difficult to determine ground based at sea unless you knew what the tide and currents were doing.[/QUOTE

This is the confusion.... if it is referenced to tide ( tut tut you will get your wrists smacked if you follow tradition)/ current makes no difference to true wind ( as I see true wind) if you start adjusting for current it then become apparent wind.
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Old 16-11-2013, 03:43   #30
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Re: terminology ........ whats your flavour ???

Taking the risk of being called a limey or pomme ( or what ever else you care to call an English man)

It would appear that there is an Atlantic divide , The ASA teach one thing the RYA another......... CF another

I suppose it does not matter as long as the captain and crew/ navigator agree on your ship.

But when discusing the finer points of tidal currents in a forum we need to have continuity

I propose ( seconder and quorum needed) ( and I am not going to be the chairman) that this thread is used as a reference to what is understood by CF members, we can even have acronyms ( requested by some of our honourable members)
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