Speed indicator

[Herb Parsons]

Knot Not a Distance

Since he got his initial question answered, and we've veered off into the realm of traditional nautical language, I'll throw another one out there.Technically, a "knot" is not a measure of distance, it's a measure of speed. The number of nautical miles you travel in an hour. That's why when you're driving, you're going 55 miles per hour, but when you're sailing (on a REALLY good day), you're going 6 knots (notice it's not 6 knots per hour).

 

[Franklin]

then

if MPH is Miles (distance) per time, then why isn't "The number of nautical miles you travel in an hour." a distance per time?In other words, if nautical miles isn't a distance, what is it?

 

[Pete]

If knots are not...

"a distance," as stated below, then why is there a scale on every chart I own showing nautical miles?

 

[Dan McGuire]

Nautical Miles is a Distance

Knots is your speed in nautical miles per hour. A nautical mile or one degree of latitude is equal to 6076 feet. A statute mile is 5280 feet.

 

[patrick]

Real minutia

From somewhere the internet:A nautical mile is a unit of distance used primarily at sea and in aviation. The nautical mile is defined to be the average distance on the Earth's surface represented by one minute of latitude. This may seem odd to landlubbers, but it makes good sense at sea, where there are no mile markers but latitude can be measured. Because the Earth is not a perfect sphere, it is not easy to measure the length of the nautical mile in terms of the statute mile used on land. For many years the British set the nautical mile at 6080 feet (1853.18 meters), exactly 800 feet longer than a statute mile; this unit was called the Admiralty mile. Until 1954 the U.S. nautical mile was equal to 6080.20 feet (1853.24 meters). In 1929 an international conference in Monaco redefined the nautical mile to be exactly 1852 meters or 6076.115 49 feet, a distance known as the international nautical mile. The international nautical mile equals about 1.1508 statute miles. There are usually 3 nautical miles in a league. The unit is designed to equal 1/60 degree [2], although actual degrees of latitude vary from about 59.7 to 60.3 nautical miles. Thus a nautical mile is a minute of latitude not a degree. A degree of latitude would equal 60 minutes and thus 60 nautical miles.I frequently use the degree markings of latitude instead of the mile scale to get a quick measure of distance. That is especially useful in flying when you are in a hurry and do not have room to unfold the chart or do not have a scale handy. You must be certain to do this only with the latitude markings and not the longitude ones since they vary in length depending on your distance from the equator.

 

[Dan McGuire]

Error Correction

In my earlier post I equated one nautical mile to one degree of latitutde. One nautical mile is equal to 1/60 of a degree of latitude or one minute of latitude.

 

[BobW]

Knots is a slang term for 'nautical miles per

hour'. So knots is equivalent to MPH (in meaning, not in measure, of course)And it's a lot easier to say!What's missing is a slang term for 'miles per hours'.Which conclusively proves how much more advanced sailors are when compared to all other travelers ;DCheers,Bobs/v X SAIL R 8

 

[OldCat]

Full Story on Knots

Go to the link at the Wikipedia. Great article, with links to more.The 1 nautical mile = 1 minute of latitude is what is taught in basic navigation -> the reality is a small amount more complicated, it varies as the earth is not a perfect sphere.Not all charts have distance scales - which is why the (very good) approximation of 1 minute of latitude = 1 nautical mile is useful and taught in nav class. That was the original definition of the nautical mile, but more accurate survey technique has required a change.Technically an international nautical mile is now 1852 meters (exact), and a knot is 1852 meters/hour.Most of the info given by various posters is correct & all we really need for navigation - but it got me thinking so I looked up the precise definitionRead the article and you will probably know more about it than you wanted, but it is a great article.

 

[Rich]

A statute mile...

...or what we know as the "mile" on land, was originally the distance a Roman soldier in Britain could cover in 1,000 paces. (And no, I can't give you a citation for where that factoid comes from).Supposedly the Metric system has its own system of latitude and longitude tied to metric measures, but I've never seen it mentioned even in European literature so I don't know what unit it would use for expressing speed over water (perhaps kilometers, as on land?)...

 

[Rick Macdonald]

Slang for 'miles per hour'

It's been so long that I don't remember when it was exactly that the US backed out of their commitment to switch from imperial to metric units. We in Canada stuck to the plan and made the switch (around 1970 or so? I was in high school then).Even so, you still hear a mixture of units every day. Miles and degrees Farenheit aren't heard so much anymore, but the more tangible feet and inches surely are. I suppose kilograms is heard in grocery stores but I'll be more or less 6 feet tall and 155 lbs soaking wet until the day I die, thank you very much.Anyway, in answer to the lack of a slang term for the wordy 'miles per hour', we've adopted the endearing term "klicks" to mean kilometres per hour. Six sylables was just too much. Even the four sylables of 'kilometres' is too much, so we call the distance measurement a klick as well.Hey - you missed your chance!Oh, aviation and maritime navigation still goes by knotical miles, altitude in feet etc, last I heard.Have you ever heard of the Air Canada 767 that ran dry of fuel and landed dead stick at an abandoned Royal Canadian Air Force Base in Gimli, Manitoba in 1983(forever known as the Gimli Glider now)? That was due to a pounds/kilograms unit mixup when fueling the aircraft in Montreal and again checked in Ottawa before departing for Edmonton....RickM...

 

[BobW]

I guess we do have a slang term

for miles per hour....... it's nothing!If I say 'I was doing 65' EVERYBODY knows what I meant ;DCheers,Bobs/v X SAIL R 8

 

[Herb Parsons]

I'll Try to 'Splain

"In other words, if nautical miles isn't a distance, what is it?"Guess I didn't make myself clear.A nautical mile is a measure of distanceA knot is a measure of speed (nautical miles per hour)Although "knot" and "nautical mile" are often used to mean the same thing, they do not.

 

[Howard]

Speed and distance...

Now we all know that a "knot" means "nautical miles per hour." If you were going 1 knot, you would cover 1 nautical mile in an hour. Therefore, a "knot" conveys the idea of both speed and distance. Knots and speed and distance have the same relationship to each other as miles per hour have to speed and distance.

 

[Fine Wine]

Nautical mile

The geographical or nautical mile is one minute of longitude measured along the equator - 6082.66 feet.British practice: Admiralty measured mile - 6080 feet or 1.8532 km.International nautical mile, official unit in the U.S.A. since 1954 - 6076.1033 feet or 1.852 km.

 

[Fine Wine]

The other longitude

Of course, I meant to write one minute of latitude at the equator...

 

[Roger1250]

absolutely amazing

The amount of collected knowledge in this group is astounding. This is certainly knot where I expected this thread to go, but it was certainly entertaining. Interestingly I did do the math and the ratio for the accepted given feet for each of the nautical and statuate mile is a factor of 1.1507575757575757575757575757576, so the general concensus of 1.15 knots would be an accurate coversion factor.One other point not (or is that knot or naut), not yet mentioned in regard to the short form of the kilometers per hour, kph, klicks is the shortend K's. as in "that guy passed me in a no passing zone doing a least 150 K's."You all have a happy Thanksgiving now!

 

[patrick]

Degrees of latitude

are always the same not just at the equator. Lines of latitude always go through both the north and south poles and thus are all the same distance per degree. Lines of latitude (oops, correction - I meant longitude) are parallel to the equator and thus the distance per degree varies all the way down to nothing at the north and south poles.

 

[Rick I]

Nautical Mile

N.M. is the length of an arc of a meridian subtended by an angle of 1' at the center of the curvature of the place. It varies in length from 6046 feet at the equator to 6108 feet at the pole. The mean length is 6080 feet and this is the standard N.M. (stolen from my real old navigation books but I don't think anything's changed in this regard since my sea-going days, everything else has changed though, don't even have to take celestial navigation at the Naval Academy anymore, it's an elective!)

 

[kendall]

knotmeter

I just consider a knotmeter as a speedometer without an odometer works easier that way!  I tried to explain to my youngest son the whole knot vs mph thing, and he still says knots per hour, guess I'm not explaining it as well as I could!  I never did care for the metric system, too easy to mess up by misplacing the decimal. The only time I use it anymore is when I'm building stairways, all the math gives decimals, so why not start with a base ten system and avoid conversion. But still, you have to admit "I was cruising at a hundred" sounds a lot more impressive then "I was only doing 60!"ken.

 

[Herb Parsons]

Wow!!

You have a boat tht does 60?? Gotta quit sailing those hurricanes!