# Knot Meter vs. GPS



## TSOJOURNER (Dec 16, 1999)

Which speed indicator should I believe: a knot meter or a hand held GPS??
My knot meter may show 2 knts, but my Garmin handheld shows 4+ knots. I like the idea that I am going faster, but which is best. ( Or does it really matter... whatever floats your boat... so to speak... )


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## Classic30 (Aug 29, 2007)

maboyer said:


> Which speed indicator should I believe: a knot meter or a hand held GPS??
> My knot meter may show 2 knts, but my Garmin handheld shows 4+ knots. I like the idea that I am going faster, but which is best. ( Or does it really matter... whatever floats your boat... so to speak... )


Your knot meter is showing "speed-though-the water" and your GPS "speed-over-ground". Completely different things.

You can do the math, but assuming you were going down river at the time, the GPS is showing a 2+ current pushing you along.. Enjoy the ride!


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## TSOJOURNER (Dec 16, 1999)

Without knowing the conditions you were sailing in 4 knots sounds more like a "normal" speed, and so seems more likely to be correct. The knot meter may be under reading because the paddle wheel is dirty or it may just need calibrating.

You can check them both by sailing between two known points and timing how long it takes and seeing if one or neither of them is correct. 

Both ussually have some sort of damping control to even out the reading, so it might be worth looking at that. Was the GPS reading steady or fluctuating a lot?

Cheers

Ian


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## TSOJOURNER (Dec 16, 1999)

So, my speed between point A and point B is best defined by the GPS?


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## sailingdog (Mar 19, 2006)

Maboyer-

A GPS will give you Speed Over Ground—SOG. The SOG is your actualy speed relative to two fixed points on earth... A knotmeter will give you Speed through the Water... which is a totally different thing. 

For instance, if you're sailing and you have two knots of current against you, the knot meter may say six knots, where the GPS will say four. Likewise, if you're sailing with a two-knot current, the knotmeter may say four knots and the GPS six.


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## JiffyLube (Jan 25, 2008)

I think the GPS is a more accurate tool for speed indication, but it's not as instantaneous as a knot meter (because you have to wait for the signal to return to the GPS from the satellites). The GPS is calculating your speed based on the distance traveled over ground, but the knot meter is calculating you speed based on the amount of times its wheel is turning in the water (directions of currents can affect those readings).


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## jzk (Feb 25, 2008)

GPS is more accurate and precise. The knot meter is important whenever sailing in a current. Then, you need to compare the GPS to the knot meter.


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## Plumper (Nov 21, 2007)

Run a measured mile and time it. Compare that with your knot meter to set in correctly. The GPS is always correct; it just isn't giving you the information you want to check your knot meter.


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## billyruffn (Sep 21, 2004)

You can also do a controlled run on a calm day in what you know is a "no current" environment where you theoretically should get the same reading between GPS and speed log. If not, there should be an electronic adjustment you can make to the speed log that will allow you to "sync" the two to each other. While on the controlled run mentioned above, adjust the speed log until it reads what the GPS is indicating. When you've done that, turn around and run back where you came from and you should have the two agreeing with each other. Repeat the process until you have them agreeing within a few tenths of a knot. 

It's a good idea to make sure the paddle of the speed log is clean and turning freely before you start the calibration exercise.


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## PBzeer (Nov 11, 2002)

I use the GPS to tell me how fast I am going between two points. I use the knot meter as an indication of the effect of changes in sail trim.


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## Plumper (Nov 21, 2007)

Trying to set your knotmeter using the GPS will only give a very rough setting. It is similar to setting your compass using your GPS. Not very accurate. The real advantage of the knotmeter is not actual speed but changes in speed. Like PBzeer says, use the knotmeter to help you refine sail trim. It will show instantaneous speed changes. Use the GPS to calculate when you'll arrive at your destination.


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## Plumper (Nov 21, 2007)

Trying to set your knotmeter using the GPS will only give a very rough setting. It is similar to setting your compass using your GPS. Not very accurate. The real advantage of the knotmeter is not actual speed but changes in speed. Like PBzeer says, use the knotmeter to help you refine sail trim. It will show instantaneous speed changes. Use the GPS to calculate when you'll arrive at your destination.


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## brak (Jan 5, 2007)

Personally, I don't have a little paddle on my boat. On all previous boats it would get clogged up by barnacles and growth in about a week and from then on become useless. So, one less hole in the hull for me. Certainly having a differential available to figure out what the current is doing is nice - but this can be done simply by knowing what your boat characteristics are and comparing those vs. what GPS shows for SOG and heading.


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## Classic30 (Aug 29, 2007)

Most people get away with just using a GPS.. because they're only interested in how fast they are going on their journey from A to B and aren't terribly concerned about sail trim or the set of the tide.

If your main interest is to get the best from the boat, a knot meter is the way to go; if your main interest is to get from A to B stinkpot-fashion, use a GPS. To determine drift on a dark night, use both.

As has been said before: They are different devices for different purposes.


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## timebandit (Sep 18, 2002)

What a bunch of BS!!!

My Gps gives me changes in speed every 1/2 second so if I make a sail trim change and look down it has noted it.

If I make a sail trim change going with the curent or against it it will show up as speed change over the ground because the speed in the water will be different.

The little paddle wheel is both old and dumb, for instance. If I sail out of a marina and head up stream on a moonless night at 6 knotts and the river running aginst me at 6 knots. The little wheel is showing 6knotts and the millage is adding up all night (say 10 hours), 60 nm. 

What the hell do I see when the sun comes up???

The same marina in the same place it was 10 hours ago.

Won't fool the GPS though!!!

AND

It will do a lot more.

Rick


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## Classic30 (Aug 29, 2007)

Rick, as was posted months ago, they are different devices for different purposes.

To use your example of heading up stream at 6 knots against a 6 knot tide, all the GPS will show you is that you're not moving. It *won't* tell you how fast the tide is running (has it peaked or not?) or whether you're doing the best you can with the boat (maybe you're only doing 4 knots into a 4 knot tide, but if you went up a gear you could do 6?..) - only that you're not getting anyplace.

Same goes for sail trim changes. The GPS will only tell you what's happening *assuming* that the current flow (if any) hasn't changed. Mostly that'll be okay, but if you happen to sail past an overfall at the same time as trying to trim the sails, you'll never know whether the boat is going sideways because of the sail change or because of a change in tide.

If you had a knotmeter *AND* a GPS, the knotmeter would show the tide running at 6 knots, but the GPS shows zero, so better go back in and wait for the tide to change.

You do really need both..


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## TSOJOURNER (Dec 16, 1999)

Hartley18 said:


> If you had a knotmeter *AND* the knotmeter would show the tide running at 6 knots, but the GPS shows zero, so better go back in and wait for the tide to change.


How does your knotmeter know the tide speed?

I don't think it does. It may measure the relative speed at which the boat is being separated from the water it sits in by movement of the boat and/or water, but does not indicate the direction or speed of water movement.

If there is a tool that measures water speed and direction, that would be the perfect companion to the GPS and obsolete the knotmeter.


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## sailingdog (Mar 19, 2006)

Andy-

If you have both a knotmeter and a GPS...any difference between the two readings is due to current effects. If the GPS says you're moving at .3 knots SOG, but the knotmeter says you're doing 4 knots through the water... you're actually sailing at four knots but against a 3.7 knot current, and effectively moving at .3 knots. Having only one or the other instrument would give you far less data. With the knotmeter, all you'd know is that you're making four knots through the water, but not what your SOG was—and if you were planning using the four knot speed, as a estimate, your calculations would be seriously borked....and if you only had the GPS, you'd only know you were making .3 knots SOG but not why.


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## TSOJOURNER (Dec 16, 1999)

The knotmeter doesn't know the tide speed or direction. You, the navigator, are the perfect companion to the GPS in figuring out the current from what the knotmeter is trying to tell you.

Here's a link to Chapter 7 of The American Practical Navigator. Go down to Section 707, "Calculating Set and Drift and Plotting an Estimated Position":

http://www.vinduemaritime.com/bowditch/Chapt-07.pdf

US Sailing also publishes a great course textbook on Coastal Piloting that gives a simpler explanation of Set & Drift calculations, although they call it a "current vector".


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## gc1111 (May 13, 2004)

I would like to point out that speed measurement by GPS is probably the least accurate information that will be provided by a GPS. This is because it is computed locally from information determined by the GPS signals. Your GPS receiver records a couple of positions and the time they were taken, then computes the speed and course. This differencing process is notorious for the error compounding that occurs. First any errors in the position are additive in computing the speed, second the difference is a much smaller number, but the errors are relative to the original position. Thus the accuracy suffers.

An example. If the accuracy of each position is 10ft. , the accuracy of the difference is only up to 20 ft. But the difference might be only 50 ft. if you are moving slowly. So the result can have a large error. There are things that can be done to mitigate this, such a keeping a running average speed, but the net result is that speed measurements with a GPS are the least accurate number that it produces.


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## EO32 (Jan 7, 2008)

gc1111 said:


> I would like to point out that speed measurement by GPS is probably the least accurate information that will be provided by a GPS.


You must have a old GPS.

Using my Garmin 76csx handheld in my car shows my speed, and speed changes within a second.

I do find direction changes take several seconds, but speed seems to be spot on and stable.


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## gc1111 (May 13, 2004)

EO32 said:


> You must have a old GPS.
> 
> Using my Garmin 76csx handheld in my car shows my speed, and speed changes within a second.
> 
> I do find direction changes take several seconds, but speed seems to be spot on and stable.


Please read what I said more carefully, I phrased it carefully to cover all - new and old - receivers. Also think about what I said about mitigation techniques, almost all receivers will use these. What do you mean by "spot on"? How accurate is that? How do you know that?

I am retired after a career as an Applied Mathematician and Computer Scientist. I know a bit about error analysis, but I do not know enough about the internals of GPS computations to make specific statements. I am simply pointing out that the basic speed calculation is prone to errors and that smoothing and statistical techniques are used to mitigate them. Just because the display is stable does not mean it is accurate down to the tenth knot many systems display.

Also note that the more frequently the speed is calculated, the less accurate it is.


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## Boasun (Feb 10, 2007)

The GPS has a built in delay of about 30 seconds. So even if you are getting spd changes every half sec, it is really every 30.5 seconds... And this is the reason you don't use the GPS to steer by.


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## BarryL (Aug 21, 2003)

Hello,

An additional thing to note about GPS is that it will be influenced by pitch and roll. If the antenna is moving because the boat is rolling, that will affect the speed display. Same thing with pitch. If the boat is pitching up and down, that will also affect the speed display. I don't believe pitch and roll have an effect on the paddlewheel.

Barry


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## jgeissinger (Feb 25, 2002)

*GPS and speed*

gc1111 is making very good points about the accuracy of gps in determining speed. Remember that what gps does in essence is to constantly triangulate your position from several distant points (satellites), to an accuracy that can vary from a few feet to several meters. So at any given moment your position is plotted at a few feet in front of where you actually are, then a few feet behind, then twice in a row several feet in front, etc. In something like a car at 60mph the speed conversion can be very accurate. In a boat at 5 knots it can show some variance even at a constant actual boat speed and still water. I use both, as others have said; to measure my progress going somewhere the gps, but sail the boat most efficiently, the digital knotmeter.


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## mikehoyt (Nov 27, 2000)

Let's not forget navigation.

If the GPS dies for some reason then knowing how fast you are travelling - even if over water - is important. Using compass, speed, chart, etc... is important for navigating.

A GPS is a nice gadget that we all depend on too much - but is also a useful tool that accomplishes a lot in one device. 

If I had only one on my boat I would probably go for GPS but for general daysailing in my own bay I usually leave the GPS off and watch my knotmeter. 

Mike


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## SailorMitch (Nov 18, 2005)

this topic is always good for starting a sh*t fight on here. it comes up at least once a year with the same results. 

Now for the next topic---what is better a tiller or a wheel???????


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## SteveInMD (May 11, 2007)

I'm sure Sailor Mitch is right, but going to waste my time and post anyway...

For cruisers a GPS alone is just fine and less maintenance, unless you are sailing in areas with a lot of current. Sailing past a buoy is a good way to see what's happening with the current.

I think you will find racers rely on a good quality paddle wheel system due to it's quick response and precision. Of course they will also have a GPS for SOG. A good paddle wheel will show you not only tenth of knots, but it will show you if your speed is increasing, constant, or decreasing before the tenths even change. This is very useful for sail trim adjustment.


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## T34C (Sep 14, 2006)

OK, I'll bite.

1) Not all sailors sail in an area that even has a current! All the generalizations about the affect of current on SOG v. STW contain a certain amount of BS.
2) Yes, pitch and yawl can still affect the little paddle wheel. (Not likely as much) It is just measuring your speed throught the water reguardless if it is forward progress or vertical progress down the side of a wave. The gps may or maynot be affected, depending on the location of the antena.
3)The little paddle wheel is just as likely to break and need some redundancy just as much as the GPS.(probably more) Just look at the original post. Additionally if the gps breaks, your prety likely to know it. If your paddle wheel is reading .1 mph wrong (10%), good luck.

Mitch- Tiller, but I have learned to really like a wheel.


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## TSOJOURNER (Dec 16, 1999)

sailingdog said:


> Andy-
> 
> If you have both a knotmeter and a GPS...any difference between the two readings is due to current effects. If the GPS says you're moving at .3 knots SOG, but the knotmeter says you're doing 4 knots through the water... you're actually sailing at four knots but against a 3.7 knot current, and effectively moving at .3 knots. Having only one or the other instrument would give you far less data. With the knotmeter, all you'd know is that you're making four knots through the water, but not what your SOG was-and if you were planning using the four knot speed, as a estimate, your calculations would be seriously borked....and if you only had the GPS, you'd only know you were making .3 knots SOG but not why.


"Current effects" - yes, I agree. But that doesn't always easily translate into what the current speed and direction is. In your example, you are talking about moving directly against a steady current where the math is simple. There are two variables each with two parts - the boat speed/direction and the current speed/direction. The GPS measures the result of the two in combination. The knot meter only measures how quickly the molecules of water under the boat are replaced by different molecules whether it is the boat or water or both moving. My point is that I think it would be far more useful to have an instrument that actually reported the current speed and direction. Of course, for low draft guys like us, it would also be nice if it could detect it a distance so we can eddy hop against the tide.


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## knuterikt (Aug 7, 2006)

Hi
Lots of opinions on this apparently.
Facts first.
A proper calibrated log will give me the speed throug water, the old fashioned way to calibrate the log is to run a known distance (1') in both directions to get a correction for the currents.
The GPS will give me speed over ground

In the are i'm sailing we have a stong NE current most of the time, the current has a slower speed near the coast. So when we are sailng NE along the coast (against the current) and against NE winds the differnce between STW and SOG give us an indication of when we should tack towards the shore again.

So I prefer to have both sources available on board, the most important thing is to know the difference between those to information sources


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## PalmettoSailor (Mar 7, 2006)

Boasun said:


> The GPS has a built in delay of about 30 seconds. So even if you are getting spd changes every half sec, it is really every 30.5 seconds... And this is the reason you don't use the GPS to steer by.


There is no way the latency in GPS is anything close to 30 seconds. NO WAY. I have a GPS in my airplane that is certified to allow flying with no visual reference to within a couple of hundred feet above the ground at over 100 mph, using only the GPS for navigation. I think even without WAAS and RAIM prediction, GPS is plenty accurate enough for a sailboat.

As to inaccuracy, GPS is least accurate in determining altitude. Position and speed are both accurate enough to support separation by Air Traffic Control. Basically, the speed ATC sees on the radar (groundspeed or SOG) is the same as I see on my GPS. "Airspeed" as shown on my instrument panel can be likened to the paddle wheel on a boat, but is critical, because if my speed through the air is too low, the wing will stop generating lift and the plane will no longer fly. Boats float no matter how slow they go. ;-)


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## TSOJOURNER (Dec 16, 1999)

You should check out the Mars Draft 925-05 if you want an affordable stand-alone unit to determine current speed and direction. The 925-05 can interface any GPS with your magnetic compass and your existing knotmeter to provide current vectors for the prevailing conditions. It has a fixed sleeve, a precision clutch and an adjustable window, and can be stored below when not in use. I'm not sure about how much wiring or networking is involved but they claim it will work with 4 different line widths. Its made in Germany by Staedtler.

Here's a link to the manufacturer's site:
925-05 Mars Draft Instrumentation Interface Unit - STAEDTLER


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## Classic30 (Aug 29, 2007)

TillerJohn said:


> You should check out the Mars Draft 925-05 if you want an affordable stand-alone unit to determine current speed and direction. The 925-05 can interface any GPS with your magnetic compass and your existing knotmeter to provide current vectors for the prevailing conditions. It has a fixed sleeve, a precision clutch and an adjustable window, and can be stored below when not in use. I'm not sure about how much wiring or networking is involved but they claim it will work with 4 different line widths. Its made in Germany by Staedtler.
> 
> Here's a link to the manufacturer's site:
> 925-05 Mars Draft Instrumentation Interface Unit - STAEDTLER


Neat! Operator error could be a problem though..  

If you have a GPS and a knotmeter determining current speed and direction is easy: In little or no wind, simply alter your heading and boat speed (whilst motoring to be practical) until the GPS shows "0 knots" - stationary. At that moment: Current speed = the reading on the knotmeter; current direction is opposite to your compass bearing.

At least that's how the cartographers do it.


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## davidpm (Oct 22, 2007)

There is a neat trick where you take the number of minutes it takes to go a mile (15 Minutes for 4 knots for example) and multiply it by the current in knots to get the number of degrees you have to steer up current to hold a course. So of the current is only 2 knots you would have to steer off the course the GPS says to go by 30 degrees (Assuming the current was at right angles to your course)

Since sailboats go so slow even a moderate current significantly changes the course we hold on the compass despite the "accurate" course computed by the GPS.

Of course if you sail where their is no current you can ignore all of this.


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## Trekka (Jul 16, 2006)

I have 3 GPS units, two of them late model WAAS enabled. Standing still I can watch the accuracy fluctuate. The variations may not mean much if one is moving a hundred feet per second, but at a measly 4 kts, the difference can be notable. All of the units allow selection of time period for speed averaging. I'd not trust anything less than a 20 second average.


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## Classic30 (Aug 29, 2007)

Trekka said:


> I have 3 GPS units, two of them late model WAAS enabled. Standing still I can watch the accuracy fluctuate. The variations may not mean much if one is moving a hundred feet per second, but at a measly 4 kts, the difference can be notable. All of the units allow selection of time period for speed averaging. I'd not trust anything less than a 20 second average.


...which means, if you're using it for sail trim, it's not going to be nearly as responsive to that tell-tale gust of wind as an expensive knotmeter.


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## timebandit (Sep 18, 2002)

I have a Garmin 276 maping gps (chart plotter)

It can read up to 12 satalites at once but usually 8.

It will navagate streets in one mode or sea in another.

Accurate?

Put a cone in the middle of a parking lot and mark as a way point. Have someone take you out about 300 yards. Use the goto function and follow the arrow back to the cone (walking). Change your direction how ever you want but the arrow just keeps pointing to the cone, just like a divining rod. Gps says arrived at destination---kick the cone over.

Low speed? GPS mounted on my motorcycle and showing 3mph. Law enforcement friends radar, would not read. Laser would --3mph

High speed? Same motorcycle, fontana motor speedway, the end of the high speed straight. GPS max speed 187 mph, speedo hold--190, radar--190 and the laser--187.

Following a track. Friends 55 foot ketch. I set way points as we left the slip at each turn from the marina down the chanel to the exit at LA Gate and out past the shiping lanes. Comming back in aginst an ebbing 2 mph tide he followed the track and I swear that if there was not a tide running counter it would have put the boat in the slip. We also received a lot of finger pointing and comments on our speed which was 5mph in a 5mph zone from boat using their knot meters for speed.

So in summation---
On my boat I have a AWD gage, knot meter with distance, depth gage, and a compass.

AWD gage---worthless in ligh air and rolling seas--faceis better.

Knot meter and log---Totally worthless in the real world.

Depth gage---I will keep that one.

Compass---Another worthless POS--just tell you what direction you boat is pointed but not the direction you are sailing.

Oh! and what about that sacred cow the sextant? I guess if you dont drop it and the weather is good and you books are up to date and you watch is accurate and your pencil is sharp and paper is dry and you remember how to do it.

While you are getting the thing out of the box I will just turn on my GPS and get the lat and lon to put that little X on my chart and be accurate within 50 ft. anywhere in the world I want to go.

Looking back I guess those instrments do really have a use---To plug up those big holes in the bulkheads.

Rick


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## SEMIJim (Jun 9, 2007)

timebandit said:


> ...
> 
> Knot meter and log---Totally worthless in the real world.
> 
> ...


Until & unless something happens to the GPS system. Perhaps you've missed all of the several warnings over the past few years about solar storm activity possibly greatly degrading the system, potentially rendering some planet-side units non-functional?

We use our GPS. We rely on it utterly _at this time_. But as our sailing skills improve, I plan to expand my knowledge and abilities by being able to survive _without_ the GPS. Will we still use it? Damn straight. But I don't like having to depend on it. It is, after all, a relatively delicate, man-made thing.

Jim


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## timebandit (Sep 18, 2002)

"But I don't like having to depend on it. It is, after all, a relatively delicate, man-made thing."

Jim

Sand box and a stick


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## bubb2 (Nov 9, 2002)

GPS or Knot meter: I quote witch ever reads the highest when the back at the dock and the guys ask how was your sail!!!!!!!!!!!1


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## gc1111 (May 13, 2004)

timebandit said:


> I have a Garmin 276 maping gps (chart plotter)
> 
> So in summation---
> On my boat I have a AWD gage, knot meter with distance, depth gage, and a compass.
> ...


Its a shame that all those years I spent navigating the Maine coast in heavy fog using only a knot meter, log, compass and chart don't seem to count as "real world" experience. I'm sorry Rick but your rant just illustrates your lack of experience.

One year I had just gotten back from Bermuda (using GPS the whole way) when my GPS and all others from that maker stopped working. "Sorry, a software bug - send it back and we will fix it." I would have been angry if it had stopped a week earlier when I was coming through the gulf stream, but I had multiple layers of backup that I knew how to use. And yes it did include a sextant and tables. So I would have made it back okay.

And what about the inlet between two islands in the Bahamas which was more than a half mile off from the GPS position - if I had really believed the GPS, I would have been in deep trouble trying to make that inlet at night. In this case it was the chart in error, but it illustrates the multiple ways things can go wrong if you rely only on a GPS position.

I use GPS, electronic charts, and radar because they make life easier. But I also know that I can get along just fine without them. Can you say the same?


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## TSOJOURNER (Dec 16, 1999)

I certainly can't say the same, and I have been sailing over 40 years! I have a portable pocket GPS, and before I cruise into my retirement I shall have another. I consider myself a good enough navigator to handle the Great Lakes, but have no desire to sail in salt water. The last time I crossed Lake Michigan I steered by the compass 2/3 of the way, and by the Sears tower the rest of the way! But I have also been out on that pond with pea soup fog, long enough ago that there was no GPS, and made my harbor using a compass, depth guage, knot meter, and charts to get me close, and the fog horn on final approach. It's a lot easier with GPS, but I do like redundant systems! I will always sail with both knotmeter and GPS, and yes, I do know the difference in readings. BTW, knots don't mean as much on this river, the river charts and mile markers are in statute miles!


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## jonlgauthier (Apr 27, 2000)

gc1111 said:


> And what about the inlet between two islands in the Bahamas which was more than a half mile off from the GPS position - if I had really believed the GPS, I would have been in deep trouble trying to make that inlet at night. In this case it was the chart in error, but it illustrates the multiple ways things can go wrong if you rely only on a GPS position.


Well, that's not the fault of GPS - it's probably the fault of the electronic charts embedded in your GPS/chartplotter. So don't blame GPS (the technology) for the failure of the chartplotter maker, or the original cartographers, who probably used sextant and a clock when they surveyed the Bahamas back in 1902 or whenever...

Or it could have possibly been due to operator error - the Bahamas charts could have been using NAD27 and the GPS was set to WGS84.


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## sailortjk1 (Dec 20, 2005)

Just for the hell of it, I will add nothing but only say, last week our GPS/Chartplotter showed us taking out a breakwall and docking on land. Thank God I have two functioning eyeballs and I know the difference between dry land and water.


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## timebandit (Sep 18, 2002)

gc1111 said:


> Its a shame that all those years I spent navigating the Maine coast in heavy fog using only a knot meter, log, compass and chart don't seem to count as "real world" experience. I'm sorry Rick but your rant just illustrates your lack of experience.
> 
> My lack of experience or your exceptional knowldge of your local sailing waters? Would you be able to do the same in San Francisco Bay with the same instraments and no local knowldge?
> 
> ...


I am a play sailor, It is not my life or my passion, just a hobbie. I also ride dirt bikes, street bikes, water and snow ski,etc. Just kinna depends on the season and the inclination.

I am in southern California and the sailing season is year round.

I might want to tow it to lake Mead for a raft up with some power boats and house boats. Where are we meeting? Just give me your lat and lon. and I will be there. Maybe San Deigo one week and the next in Los Angles Harbor. Never far away from land that I cannot see it. If I do go way out just for fun and get lost I just look at the sun and aim east untill I bump into land.

Rick


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## gc1111 (May 13, 2004)

timebandit said:


> I am a play sailor, It is not my life or my passion, just a hobbie. I also ride dirt bikes, street bikes, water and snow ski,etc. Just kinna depends on the season and the inclination.
> 
> Rick


The fact that you are a play sailor was pretty evident from the beginning. Making your entry in a large red font cannot hide that. A beginner making great proclamations about the value of various pieces of gear gets very little respect.

By the way, I could do and have done the same thing in San Francisco Bay. I lived in the Bay area in the early sixties and did a lot of sailing on the bay with only compass and knotmeter.

And Maine is not my local sailing waters. I live on the South Shore of Long Is. which has clear weather and muddy bottoms which Maine definitely does not have. I have taken many summer cruises Down East though.


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## camaraderie (May 22, 2002)

Well...this is an old discussion but I will state that a single $100 gps is the most valuable navigation tool on board though radar would be a close second. I sailed for many years without anything but a compass and depth sounder until the wonders of Loran opened new horizons...and was well versed in coastal navigation techniques. So...I agree that it is possible to sail anywhere without a GPS. There is a mindset however that seems to say that the "old ways" are somehow better than the new ways and one had better be versed in the old ways to be safe. I completely disagree and feel that ALL you really need these days is a GPS and a depth sounder and charts...with multiple redundancy on the GPS...and that you will as a result be safer than someone who relies on a single GPS and coastal techniques or a sextant. Just because something is old and tried and true, doesn't mean it is the best or necessary. Some things still are...like paper charts..and Tayanas!


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## sailaway21 (Sep 4, 2006)

Let the record show that it was not I that mentioned the market for Tayanas and sextants in the same paragraph! (g)

I'll quibble with Cam's ordering by stating that the fathometer has saved more vessels than anything other than the eyeball. Radar is certainly the next most valuable navigation and collision avoidance tool afterwards. If you have those two devices you can probably spend many safe years at sea with little else but a compass and the ability to perform dead-reckoning.

As usual, Cam misstates the position of us traditionalists. It's not that the old ways are better than GPS it is that those schooled in the old ways are better navigators than those who rely more strongly on GPS. The GPS-assisted grounding is a fact of life. Those who continue to tout it's capabilities as a panacea for lack of basic piloting and navigation skills do the maritime community a disservice. I'd encourage everyone to use their GPS but they're going to be disappointed if they think that I'll describe them as navigators. If they were as familiar with DMAHC Pub. 226 (http://www.nga.mil/MSISiteContent/StaticFiles/Files/HoMCA.pdf) as they were with their GPS owner's manual I might be inclined to listen more respectfully.


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## bobwebster (Jan 25, 2005)

Plumper said:


> Run a measured mile and time it. Compare that with your knot meter to set in correctly. The GPS is always correct; it just isn't giving you the information you want to check your knot meter.


This is true if there's no wind, no current, and no waves.

The GPS is much more accurate, but has a bit of a time lag (2-3 seconds).

You can use the GPS to calibrate the knot meter on a calm day, even if there is a current. Just drive the boat in a wide circle (or two) at constant speed, and note the maximum and minimum speed shown on the GPS. Half way in between is the precise speed through the water.


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## camaraderie (May 22, 2002)

Like a moth to the flame!


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## sailaway21 (Sep 4, 2006)

camaraderie said:


> Like a moth to the flame!


I was attracted by the glow of your enflamed plumage itself!


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## SEMIJim (Jun 9, 2007)

sailaway21 said:


> I was attracted by the glow of your enflamed plumage itself!


/me nervously eyeballs his TMI gauge...


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