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Old 11-01-2015, 06:21   #1
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Miles over ground or over water?

Hi everyone,
I need to prove to the insurance that I have enough experience to extend the areas allowed for navigation, so I am religiously recording all trips, but noticed that there is a significant discrepancy between the boat log that tracks over water, and the gps log of bad elf/navionics that record over ground.
What is the method mostly used?
Thank you for the clarification.
Cheers
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Old 11-01-2015, 06:38   #2
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Re: Miles over ground or over water?

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Originally Posted by homerobarros View Post
Hi everyone,
I need to prove to the insurance that I have enough experience to extend the areas allowed for navigation, so I am religiously recording all trips, but noticed that there is a significant discrepancy between the boat log that tracks over water, and the gps log of bad elf/navionics that record over ground.
What is the method mostly used?
Thank you for the clarification.
Cheers
Distance over ground. Don't overthnk this.

Bill
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Old 11-01-2015, 06:41   #3
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pirate Re: Miles over ground or over water?

I would have thought Nautical miles would be required.. that extra 224yds makes all the difference...
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Old 11-01-2015, 06:48   #4
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Re: Miles over ground or over water?

I'd go with the one most beneficial to me, as the wind is always coming from where I want to go, and the current against me, I'd assume it's the log that shows a higher number?
Actually whatever the difference, I'd think it's a calibration issue.


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Old 11-01-2015, 08:29   #5
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Re: Miles over ground or over water?

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Originally Posted by a64pilot View Post
I'd go with the one most beneficial to me, as the wind is always coming from where I want to go, and the current against me, I'd assume it's the log that shows a higher number?
Actually whatever the difference, I'd think it's a calibration issue.


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I would use either chart or GPS data as the most accurate. The crappy paddle wheel knot-logs are never accurate. Mine never agrees with the GPS and I know its error is different on port or stbd tack.

Do you intend to use the data also to get your USCG credentials? If so, download the small vessel form for recording your 'days of service'. The CG is not concerned about how far you have gone but rather how many service days per year.
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Old 11-01-2015, 09:01   #6
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Re: Miles over ground or over water?

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Originally Posted by a64pilot View Post
Actually whatever the difference, I'd think it's a calibration issue.
not necessarily. It maybe result of a current, and it maybe result of a sailing in swell.

Anyway, for the original poster: only 'over ground'
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Old 11-01-2015, 10:08   #7
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Re: Miles over ground or over water?

Quote:
Originally Posted by homerobarros View Post
Hi everyone,
I need to prove to the insurance that I have enough experience to extend the areas allowed for navigation, so I am religiously recording all trips, but noticed that there is a significant discrepancy between the boat log that tracks over water, and the gps log of bad elf/navionics that record over ground.
What is the method mostly used?
Thank you for the clarification.
Cheers
Ask the insurance company which one they want. If they don't care, give them the one that is to your advantage.

I personally log both. It can be useful at times to have that data when navigating through areas with unfamiliar currents. As far as logging the travels of the boat and my own personal miles, I use distance over ground.
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Old 11-01-2015, 10:12   #8
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Re: Miles over ground or over water?

For insurance? whichever one is the highest! They just need something for their file....
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Old 11-01-2015, 10:19   #9
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Re: Miles over ground or over water?

At sea there is almost always a , sometimes quite bi, difference between SOG and STW because of the tide current.
For navigation mosty teh SOG or COG is important because thats what brings you to a harbour but for teh sailed distance STW gives the real sailed distance.

Example. In the past I often saild on the river Ijssel in Holland. That river alwauys harts a current of 4-6 Km/h .
When sailing it happened quite often that when cruising close hauled I stayd almost exactly in front of the Harbour entrance although sailing at about 8-9 Km/h so 4-4.5 knots for an hour or three.
Interesting because I never needed to sail home after a short sail !

So , to my opinion its the STW what is giving your experience but only if your log is calibrated. SOG does not give the real sailed distance.
But I doubt an insurance man does understand .
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Old 11-01-2015, 10:24   #10
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Re: Miles over ground or over water?

I can't imagine that the insurance company could care less - they just want a realistic view of your experience. I would go for the one which is easiest and be consistent (ie don't pick and choose the one which gives the highest mileage) but tell the insurance what you have done when you submit the data. That way there can't be any arguments later.
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Old 11-01-2015, 11:02   #11
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Re: Miles over ground or over water?

On the Columbia River our current ranges from 0 - 6 kts. During spring melt it's quite common to sail at up river dodging driftwood and gaining no ground... Same thing happens in the San Juan's or Gulf Islands with tidal currents if one doesn't plan their route correctly. I'd say it's good helm practice sailing against the current and count the miles through the water.
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Old 11-01-2015, 11:27   #12
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Re: Miles over ground or over water?

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Interesting because I never needed to sail home after a short sail !
Or even a long one~ Wonderful & a great observation, like the following one about the Columbia River.
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Old 11-01-2015, 11:40   #13
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Re: Miles over ground or over water?

Don't ask the insurance company and don't use statutory miles. Using nm based on over-ground is conventional and anything else may raise inferences about your experience. I went through the same thing. First they wanted my "resume", then they had some questions. In the end I got great nav limits, but with the requirement that I must be on board, unless slipped at a location the insurance company has approved, or unless a licensed captain and crew pre-approved by my insurer has command of my boat. (There are also some limits regarding named storms during hurricane season when south of about Ensenada.)
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Old 11-01-2015, 12:16   #14
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Re: Miles over ground or over water?

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Originally Posted by Suijin View Post
Ask the insurance company which one they want. .........
Simple and to the point.

But will they just take your word for it? If not, you don't have to log any miles just tell them what they want to hear.
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Old 11-01-2015, 12:25   #15
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Re: Miles over ground or over water?

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Distance over ground. Don't overthnk this.

Bill
use water distance for experience, tacking upwind is more sailing experience then over ground. use distance made good for navigation. pretty simple.
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