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Old 01-08-2011, 13:31   #16
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Does tacktick use sog and cog for true wind calculations? I was under the impression they only used speed through water?
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Old 01-08-2011, 15:01   #17
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Re: Tacktick Instruments

SOG is needed to do true wind speed calculation but if you didn't have GPS you would be stuck using speed through the water for true wind speed. In a strong current it would throw off true wind speed using speed through the water..
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Old 01-08-2011, 23:21   #18
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Quote:
Originally Posted by Pblais
SOG is needed to do true wind speed calculation but if you didn't have GPS you would be stuck using speed through the water for true wind speed. In a strong current it would throw off true wind speed using speed through the water..
While that's all true, do you know if Tacktick actually uses SOG if it's available? A standard tacktick setup doesn't include a gps, so "true" wind speed on a standard tacktick is based only on speed through water and won't take current into account. Does the calculation suddenly change when you wire in an nmea gps SOG?
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Old 02-08-2011, 08:18   #19
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Re: Tacktick Instruments

The NMEA unit can take NMEA inpout from your GPS or you can use the TackTick wired GPS. There is no such thing as a "Standrd setup". As sensors or displays are added to the network they automatically share data as soon as they join.

Here is what the NMEA unit can receive and do something with:

DBT, DPT, HDG, HDM, MWV, RMB, RMC, VHW, VLW, VWR

Here is what it transmits:

DPT, GLL, HDG, MTW, MWV, RMB, RMC, VHW, VLW, VWR


If you have the speed log it does transmit VHW as well. I don't know any way to compute current unless you know the direction of the boat relative to the current and then you can trig the value easily. The boat can't measure the direction of the current.
All this is predicated on having the required inputs. So if you don't have a Tacktick depth sensor you won't get depth data. The transmitted RMC sentence would have SOG. The M100 display computes the true wind. If you don't have a NMEA device the display won't display anything for true wind or most of thre rest of the settings other than apparent wind in several formats with repsect to time.
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Old 02-08-2011, 09:39   #20
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Re: Tacktick Instruments

Quote:
Originally Posted by Pblais View Post
The NMEA unit can take NMEA inpout from your GPS or you can use the TackTick wired GPS. There is no such thing as a "Standrd setup". As sensors or displays are added to the network they automatically share data as soon as they join.

...
All this is predicated on having the required inputs. So if you don't have a Tacktick depth sensor you won't get depth data. The transmitted RMC sentence would have SOG. The M100 display computes the true wind. If you don't have a NMEA device the display won't display anything for true wind or most of thre rest of the settings other than apparent wind in several formats with repsect to time.
By "standard setup", I meant one of the packages sold by Tacktick. These don't come with GPS, though a GPS antenna can be purchased separately from them.

The M100 display does show true wind without a GPS input. In fact, according to the Tacktick manual, it always calculates the "true wind" based only on the speed through the water, not the SOG.

Quote:
The True Wind Speed with respect to the vessel, calculated
by the display taking into account the vessels speed through
the water. Both Apparent Wind Speed, Angle and Boat
Speed must be available for this calculation
I believe that this is actually quite typical of wind instruments. I'd be interested in proof of examples where this isn't the case.

Yes, I know that this isn't ideal, but it seems to be the norm. For the OP, it means that wiring in the NMEA will give an SOG display on the tacktick system, but it won't change any of the displayed wind values.

I have such a system with the NMEA and the only real value I get out of it is that my autopilot can read wind from the tacktick and steer to apparent wind angle instead of to a waypoint or compass direction. If your autopilot won't do this, then you may not get your money's worth out of installing the NMEA as the tacktick display only acts as a repeater for info that's available elsewhere.

The exception to this would be true wind direction and calculating headers and lifts if you have a compass on the NMEA system. I don't use this functionality as of yet, though, and most cruisers wouldn't spend too much time with it. Could be great for racers, though.
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