Astronomy

Defining a nautical mile

Defining a nautical mile

Astronomy is new to me so my question might be stupid: I read that a nautical mile is defined as one minute of latitude along any line of longitude. What if it was the other way round, i.e. one minute of longitude along any line of latitude? Would it make any difference?


Yes, very much so.

The lines or circle of constant longitude always form a great arc which intersects with the poles; thus it always has the same length. A circle of constant latitude varies in circumference: the largest is at the equator while it has intermediate length at intermediate latitudes and no length anymore when you reach the pole.

See e.g. that image from wikipedia and follow a circle in longitude, thus from North to South. And compare the different sizes of different circles for different lattitudes (thus the circles which are parallel to the equator)

Mind though that the nautical mile is no longer defined via the fraction of the polar circumference of Earth. It is defined as exactly 1852m in length, and thus can in principle be determined as accurately as one can measure time (1852 / 299 792 458 seconds).

In earlier times it was a MUCH easier task to determine a difference in latitude as it directly relates to the (culmination) height of celestial objects above the horizon. It was VERY DIFFICULT to impossible to determine difference in longitude unless you had a very accurate clock and an almanach of the rise and set times of celestial objects.


What is the difference between a nautical mile and a statute mile? And what is a knot?

According to the Encyclopedia Britannica a nautical mile used to be based on the curvature of the earth and was approximately equal to one minute (arc segment) of latitude along a meridian (longitudinal line running from north to south). The British nautical mile was set to 6,080 feet while the US nautical mile was set to 6080.20 feet. However, in 1929 the nautical mile was redefined to exactly 1.852 km (approximately 6076.11549 feet) at an international conference held in Monaco, although the US didn't make the conversion until 1954.

1 nautical mile = 1.1508 statute miles or 1.852 km.

A "knot" (speed measurement, not the kind you tie in your shoe laces) is equal to one nautical mile per hour.

1 knot = 1.15 miles per hour.

There are basically two different categories: nautical units and statute units. A few times early on in my aviation career I mixed the two (especially easy if you fly in a plane that uses mph but you measure nautical miles on your sectional) and it will yield inaccurate numbers, which can be pretty dangerous, depending on the calculation you are doing. These are the three main kinematic units that relate to motion of each category and values you can use for conversions:

Category: nautical/statute (conversion values)

Distance: nautical miles/statute miles 1/1.15

These all follow the equation distance = speed * time (as long as you do not mix and match the category (nautical units with statute units or vice versa).

Historically speaking, the nautical units were used by sailors because it was just more practical -- one nautical mile was originally defined as one minute of latitude (lines of latitude are the ones that slice the earth horizontally -- think "flatitude"), a distance which is relatively constant (although not totally so due to earth's ellipsoid shape, but much more so than minutes of longitude which vary greatly). This was more convenient for sailors to use than statute miles because latitude (as well as longitude) was frequently used to define position so it was easier to use for dead reckoning and navigation. Lines of latitude one degree apart are about 69 statute miles apart on the surface of the earth (varying slightly depending on your location on the surface of the earth), so one minute of latitude (1/60th of a degree of latitude), is about 1.15 statute miles apart on the surface of the earth (69 statute miles/60, because a minute is 1/60th of a degree). Since a nautical mile is defined as the distance of 1 minute of latitude, it turns out that 1 nautical mile is equal to 1.15 statute miles. The actual value now is set at about 1.15078 statute miles because the nautical mile was redefined to be exactly 1852 meters (now internationally accepted). Etymologically, the term derives from sailors counting the number of knots in the rope that unspooled from the reel of a chip log (basically a spool of rope) in a specific time. Aviation follows many naval conventions, nautical units included.

When you think of miles in normal life (20 mile drive, a mile run, etc.) those are all statute miles. Usually in aviation as well as in naval applications the units belong to the nautical category (20 nautical mile flight, 120 ktas (knots true airspeed)). Recently, however, some plane manufacturers have made a move towards using statute units in their manuals/avionics so keep an eye out for units, especially on more modern planes. As far as the aviation systems (what category weather reports use and what controllers use), everything is in the nautical category except for measuring visibility (you would hear wind readings at 10 knots from 160 degrees for example but a visibility report at more than 10 statute miles for example).

A similar important distinction (not related to statute vs nautical) is that when you READ angles (degrees on a winds aloft forecast or a METAR) the degrees are usually with reference to TRUE north (for flight planning purposes). When you HEAR angles (ATIS report, controller wind report) the degrees are usually with reference to MAGNETIC north. Anyway back to nautical/statute.

If your plane does use statute units there is most likely a statute mile side of your plotter (so you can measure statute miles on your sectional as well as nautical miles) -- use this instead of trying to convert the units it will save you time and mistakes. Also most airspeed indicators can read both knots and mph, although the outside ring is the one belonging to the category that is most likely dominant in the manual (in values for cruise speeds, etc) -- in this case mph.


What is a nautical mile, and how does it differ from a normal mile and a kilometer?

A nautical mile is based on the circumference of the planet Earth. If you were to cut the Earth in half at the equator, you could pick up one of the halves and look at the equator as a circle. You could divide that circle into 360 degrees. You could then divide a degree into 60 minutes. A minute of arc on the planet Earth is 1 nautical mile. This unit of measurement is used by all nations for air and sea travel.

A knot is a unit of measure for speed. If you are traveling at a speed of 1 nautical mile per hour, you are said to be traveling at a speed of 1 knot.

A kilometer is also defined using the planet Earth as a standard of distance. If you were to take the Earth and cut it in half along a line passing from the North Pole through Paris, and then measure the distance of the curve running from the North Pole to the equator on that circle, and then divide that distance by 10,000, you would have the traditional unit for the kilometer as defined in 1791 by the French Academy of Sciences.

A nautical mile is 1,852 meters, or 1.852 kilometers. In the English measurement system, a nautical mile is 1.1508 miles, or 6,076 feet.

To travel around the Earth at the equator, you would have to travel (360 * 60) 21,600 nautical miles, 24,857 miles or 40,003 kilometers.


Also called International Nautical Mile, it is a unit of measurement equivalent to 1.852 kilometers or 6076 feet. It replaced the British nautical mile of 6080 feet and United States nautical mile of 6080.20, through an international agreement held in Monaco in 1929.

According to US National Institute of Standards and Technology (NIST), “the international nautical mile of 1852 meters (6076.115 49…feet) was adopted effective July 1, 1954, for use in the United States. The value formerly used in the United States was 6080.20 feet = 1 nautical (geographical or sea) mile.”

Nautical mile is based on the circumference of the earth and is used for sea or air travel. Suppose you cut the earth into half at the equator, pick half of it and look through as a circle. You then divide the circle into 360 degrees and further sub divide a degree into sixty minutes. A minute of an arc of the earth is equivalent to one nautical mile.This means that if you travel around the Earth at the equator, you would cover a total of 21,600 nautical miles (360 x 60).

A knot

The term knot dates back from the 17th Century when ancient mariners gauged the speed of their ship using a device called “common log” or chip log. In this method, knots were tied at uniform intervals in a rope which had a piece of slice shaped wood at the end. The wood was then tossed behind the ship. As the vessel moved, the rope rolled out freely for a specific time and then the number of knots were counted and used in calculating the speed of the vessel. The speed was said to be the counted number of knots.

After standardization of nautical miles in 1929, knot was agreed to be its standard unit of measuring speed, calculated based on time and distance.

Up to date, knots are used in navigation and aviation, normally shown on aircraft’s airspeed indicators and is expressed in terms of nautical miles per hour. For example, if you are moving at a speed of 1 nautical mile per hour, we say you are moving at a speed of I knot.

The Mile

The concept of mile originated from the Ancient Roman times. The Romans used to put mileposts on their roads which they used to measure distance by using a unit called mille passum, a Latin word meaning a thousand paces. Each pace was estimated to be five Roman feet, meaning one thousand paces was equivalent to 5,000 Roman feet, about 4,850 of the modern feet.

Around the year 1500 in London, mile was defined as eight furlongs. A furlong is an old English unit of length equivalent to 625 feet. During the reign of Queen Elizabeth I, 280 feet was added to the 5,000 feet of original mile, under a statute of 1593 that increased the length of a furlong to 660 feet, hence the current 5280 feet per statute mile.

Converting Knots into Kilometers per Hour

Speed in kilometers per hour is the distance in kilometers traveled in exactly 3,600 seconds. If one kilometer is traveled in one hour, we express it as 1 km/hr.

Several calculation tools have been created to ease the work of conversion in different units.

For example, the Wind Speed Conversion Table below makes it easier to convert knots into miles or nautical miles per hour and vise versa.

1 Knot = 1 Nautical Mile per hour
1 Nautical mile = 6076.12 ft. = 1852 m
1 Statute mile = 1760 yards = 5280 feet

Why Nautical Mile is Longer than Mile

Nautical mile is measured based on the earth’s circumference and is equivalent to one minute of latitude.

A mile is based on land measurement which tends to be shorter than the circumference . The difference is brought about by the fact that Earth is not a perfect sphere but tends to be flattened at the poles.

In converting statute to nautical mile, we use factor 1.15, though it does not provide accurate results.

For Example

A statute mile = 5,280 feet

This means that the result is 4 feet shy from the actual figure of 6,076 feet of nautical mile .

Prearranged tables and converters like Bowditch’s Table 20 can be used to give more precise results.

Nautical Charts

Since nautical miles follow lines of longitude, they are very useful in navigation. Sailors and aviators have since come up with nautical charts that serves as graphical representation of the Earth and focuses on the areas of water.

These chart uses one of three map projections: polyconic, gnomyc and Mercator. Nautical charts make navigation easier in open waters making it a very important tool in shipping and exploration.

They may be in either printed or electronic navigational form. Technological advancements have made paper charts readily available, and can be printed “on demand” . This has made the work of sailors and mariners easy since they will be up to date with the most accurate information necessary for their travel.

Conclusion

Both statute and nautical miles are units of distance but are derived and used differently.

A mile is a unit of length on land that is equivalent to 5,280 feet and is part of United States standard units of measure. When compared with metric system, a mile is roughly 1,609 meters and it is abbreviated as m

A nautical mile is distance unit used for both sea and air travel and is equal to 1.151 miles or 1,852 meters. It is based on a minute of arc on the Earth’s sphere, with 3600 seconds of arc per degree longitude. It is abbreviated as nm.

Whenever you are using geographical charts, you should be sure of the distance measurement being used. This is because different charts use different measurements. Four measures commonly used on charts include:


Definitions for nautical mile nau·ti·cal mile

A unit of length corresponding approximately to one minute of arc of latitude along any meridian. By international agreement it is exactly 1,852 metres (approximately 6,076 feet).

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The nautical mile is a unit of length that is about one minute of arc of latitude measured along any meridian, or about one minute of arc of longitude at the equator. By international agreement it has been set at 1,852 metres exactly. It is a non-SI unit used especially by navigators in the shipping and aviation industries, and also in polar exploration. It is commonly used in international law and treaties, especially regarding the limits of territorial waters. It developed from the sea mile and the related geographical mile. The nautical mile remains in use by sea and air navigators worldwide because of its convenience when working with charts. Most nautical charts use the Mercator projection whose scale varies by about a factor of six from the equator to 80° latitude, so charts covering large areas cannot use a single linear scale. The nautical mile is nearly equal to a minute of latitude on a chart, so a distance measured with a chart divider can be roughly converted to nautical miles using the chart's latitude scale.


Nautical Miles vs Miles

In 1929, the international nautical mile was defined by the First International Extraordinary Hydrographic Conference in Monaco as 1,852 meters.

Imperial units and United States customary units used a definition of the nautical mile based on the Clarke (1866) Spheroid. The United States nautical mile was defined as 6,080.20 feet (1,853.24 m) based in the Mendenhall Order foot of 1893. It was abandoned in favor of the international nautical mile in 1954.

The Imperial nautical mile, often called an Admiralty mile, or more correctly, an Admiralty measured mile, as defined by its relation to the Admiralty knot – 6,080 imperial feet per hour – so 1 imperial nautical mile is about 1,853.181 meters. It was abandoned in 1970 and, legally, references to the obsolete unit are now converted to 1,853 meters.

If you are still uncertain about the difference between nautical miles vs miles, come aboard Yacht La Pinta , and it will all be clear right away. Picture the open ocean before you, amazing wildlife roaming freely around you, and your worries far behind. Every concept, simple or complex, will suddenly have a new meaning and the nautical miles you will be traveling around the Galapagos Islands, will be filled with the most amazing memories.


Nautical Astronomy

a branch of practical astronomy that answers the needs of navigation. Nautical astronomy is concerned with developing methods for determining from celestial bodies and navigational, artificial earth satellites the position of a ship at sea and corrections for course-indication instruments. Nautical astronomy is part of the science of navigation.

The position of a ship at sea, that is, its geographic latitude ϕ and longitude &lambda, is determined by measuring the altitudes of celestial bodies over the visible sea horizon or over the plane of an artificial horizon created on the ship by different methods. The use of angle-measuring devices with an artificial horizon has expanded the possibilities for determining ship positions by astronomical means and has also increased the precision in measuring altitudes of celestial bodies.

Each value h of the true altitude of a celestial body yields one equation for determining the ship&rsquos coordinates, so that at least two measurements of altitudes of celestial bodies are required to determine a ship&rsquos position at sea. The solution of the spherical triangle with vertices at the celestial pole, the zenith of the observer, and the position of the star&mdashthat is, the parallactic or astronomical triangle&mdashleads to the equation

where ø and tGr are the declination and the Greenwich hour angle of the celestial body, respectively. The values of &delta and tGr are selected from a marine astronomical almanac for the moments of observation. The longitude &lambda is measured eastward from the Greenwich meridian: tGr + &lambda = tloc is the local hour angle of the celestial body. When the celestial body is on the meridian of the observer in upper culmination (tloc = 0), equation (1) yields the solution ϕ = &delta ± (90° - H), where H is the altitude of the celestial body in upper culmination, called the meridian altitude. The minus sign is taken for a transit of the celestial body northward from the zenith.

If equation (1) is solved for t ioc, then we obtain the equation

(2) cos tloc = sin n . sec ø . sec &delta - tan ø . tan &delta

Knowing the latitude ϕ of the position, we can also obtain the longitude &lambda = tloc &mdash tGr using equation (2).

It is possible to determine both the latitude and longitude of a position from two measurements of altitude. With a larger number of measurements the accuracy of the determination can also be evaluated. Using what is called the estimated ship position, that is, the coordinates (ϕe, &lambdae) of the position found graphically or analytically with respect to the course angle and distance covered (dead reckoning), we can represent each of the equations obtained in the form of an error equation or geometrically interpret each equation as an altitude position line. The position-line equation has the form

In order to construct the position line, the estimated ship position (ϕe,&lambdae) is made the origin of coordinates (see Figure 1), with the latitude increment &Deltaϕ plotted along one axis and the corresponding range increment &DeltaW = &Delta&lambda . cos ϕ along the other axis. If the difference &Delta h = h &mdash he between the altitude of the celestial body found by observation and the estimated altitude calculated from the estimated coordinates is plotted from the estimated position in the direction determined by the azimuth A of the celestial body, then a point K is found, called the intercept. The position line passes through the intercept in the direction perpendicular to the azimuth of the celestial body.

The ship position is determined by the intersection point of the position lines of two stars that are continually observable. For a large number of observations, the position lines as a rule do not intersect at a single point but form an error figure. The most probable ship position can be found from this figure either by a graphical method or analytically.

The correction for course indicators is determined by comparing the observed bearing of a celestial body and the azimuth A of this body, calculated from its known declination 8, hour angle tloc = tGr + &lambda, and the latitude of the observation position. The azimuth A can be calculated from the equation

(4) cot A = cos ø . tan &delta . cos tloc - sin ø . cot tloc

Whenever the altitude of a celestial body is measured simultaneously with the bearing of the body, the azimuth can be calculated using either of the equations

(5) sin A = cos &delta . sin tloc . sec h

(6) cos A = sec ø . sin &delta . sec h - tan ø . tan h

Special tables for the calculation of the azimuth of a celestial body have been published.

The altitude of a celestial body over the visible sea horizon is measured by a sextant.

To determine the altitude h of a celestial body over the true horizon the reading obtained on the scale of the sextant is corrected by introducing the instrumental correction of the sextant, an index correction, and corrections that take into account the dip of the visible horizon, refraction, and the half-diameter and the parallax of the celestial body.

Historical survey. The positions of celestial bodies were already used in remote antiquity for orientation at an unknown position and for determination of the direction of travel. The growth of industry and trade and the expansion of navigation associated with this growth resulted, beginning in the 15th century, in the development of methods and instruments for determining a ship&rsquos position on the open sea. Astronomical instruments suited for shipboard observations of stars, including angle rods, reflecting quadrants, astrolabes, and armillary spheres, became widespread. Ephemerides of the sun and planets, which are necessary for carrying out observations, were calculated. At this time, only the latitude of a position could be determined from astronomical observations. In the 16th and 17th centuries, methods were proposed for determining longitude based on observations of the angular distances between the moon and stars and observations of the eclipses of Jupiter&rsquos satellites. A precise method for determining the longitude of a position based on the calculation of the difference between the local hour angle of a celestial body and its value at the moment of observation for the Greenwich meridian (&lambda = tloc &mdash tGr) was introduced in nautical astronomy only in the second half of the 18th century, with the construction of the chronometer.

A theory for the combined determination of latitude and longitude was developed in the early 19th century. In 1808 the German mathematician K. Gauss proposed a method requiring the solutions of five equations. In 1824 the Russian geodesist F. F. Shubert published a new method for the joint determination of ϕ and &lambda. These methods, however, proved to be unsuitable for practical application. In 1843 the American seaman T. Sumner published a method for determining a ship&rsquos position based on the fact that the position circle corresponding to the value of a measured altitude, that is, the circle of equal altitudes, can be represented over a short distance by a straight line on a map. He constructed altitude position lines by means of the points at which these lines intersect two parallel lines near the parallel of latitude of the estimated position. The Russian seaman A. A. Akimov proposed a different method, published in 1849, for constructing the position line using the single point of intersection of the position line with the estimated parallel of latitude and the direction of the position line. The perpendicularity of the altitude position line and the direction to the star was first used in this method. In 1875 the French seaman M. Saint-Hilaire proposed a method for drawing the altitude position line through a specific point and perpendicular to the direction to the star. This method continues to be used in the 20th century. The Soviet scientists N. N. Matusevich and V. V. Kavraiskii contributed much to the development of modern methods of nautical astronomy and the systematic application of the generalized method of position lines to the solution of astronomical problems.


Using Nautical Miles

Today, one nautical mile still equals exactly the internationally agreed upon measure of 1,852 meters (6,076 feet). One of the most important concepts in understanding the nautical mile though is its relation to latitude. Because a nautical mile is based on Earth’s circumference, an easy way to understand the calculation of a nautical mile is to imagine the Earth being cut in half. Once cut, the circle of the half can be divided into equal portions of 360°. These degrees can then be divided into 60 minutes. One of these minutes (or minutes of arc as they are called in navigation) along a great circle on Earth represents one nautical mile.

In terms of statute or land miles, a nautical mile represents 1.15 miles. This is because one degree of latitude is approximately 69 statute miles in length. 1/60th of that measure would be 1.15 statute miles. Another example is traveling around the Earth at the equator to do this, one would have to travel 24,857 miles (40,003 km). When converted to nautical miles, the distance would be 21,600 NM.

In addition to its use for navigational purposes, nautical miles are also still significant markers of speed as the term "knot" is today used to mean one nautical mile per hour. Therefore if a ship is moving at 10 knots, it is moving at 10 nautical miles per hour. The term knot as it is used today is derived from the previously mentioned practice of using a log (a knotted rope tied to a ship) to gauge the speed of a ship. To do this, the log would be thrown into the water and trailed behind the ship. The number of knots that passed off of the ship and into the water over a certain amount of time would be counted and the number counted determined speed in “knots.” Present-day knot measurements are determined with more technologically advanced methods, however, such as mechanical tow, Doppler radar, and/or GPS.


Defining a nautical mile - Astronomy

The Nautical Mile in Freeport is one of my favorite places to enjoy an afternoon on the water. An odd combination of restaurants and workboats, open-air bars and fish markets, live music and foghorns it’s a blend of nautical charm and street fair revelry I find hard to resist.

About the Name

When I was a kid and before I ever came here I was stumped by the name. I just couldn’t comprehend the double meaning and kept wondering why anyone would want to go see a mile. I get it now, but just in case you don’t…

The Nautical Mile is the unofficial nickname for Woodcleft Avenue, the road that runs along side Woodcleft Canal in Freeport.

Roughly a mile long and lined on both sides with all manner of maritime mayhem, it is called The Nautical Mile because of its length (don’t tell anyone, but it’s really about 25% short) and its character.

The look and the feel

If you haven’t been here in a while you may be in for a surprise.

Thanks to a successful revitalization effort by the village of Freeport, the present day Nautical Mile is a far cry from the old days.

You might remember flooded streets and broken sidewalks. Now you’ll find a beautiful brick esplanade, park benches, planters, a fountain and attractive outdoor museum displays.

Although the Nautical Mile is now more visitor friendly it hasn’t turned into a tourist trap.

After all, it is home to Freeport’s charter and commercial fishing fleet, and is the center of one of Long Island’s oldest maritime communities.

Behind the cosmetic upgrades is where the fishermen work. In other words, it still smells like fish--In a good way of course.

Things to Do

The Nautical Mile is alive with the sights, sounds, and smells of the sea. Like the neighborhood park it’s not so much a place to be entertained, but a place to entertain yourself.

Walk the Esplanade

On a sunny day you can walk the esplanade for hours (well, I can anyway).

I like to take it all in and I do a good bit of people watching too. My first stop of the day is always one of the outdoor eateries.

I’ll find a place that isn’t too crowded, belly up to the bar and have a drink. Beer, Coke, whatever, and if it’s around lunchtime I might have a light snack. All the while I’m enjoying the boat traffic up and down the canal.

There’s usually a band playing and if they’re any good I’ll stick around until they take a break. Then it’s off to the next place and the next band.

Restaurants

Dinner is always on my Nautical Mile to do list. There’s no shortage of restaurants here and they serve more than just fish--you can get whatever you’re in the mood for and then some.

Here are some recommendations, but by all means do some exploring. There are almost 2 dozen restaurants on the Nautical Mile each with a personality all its own:

Bracco’s Clam and Oyster Bar
Bracco’s is very casual and has quite a large outdoor dining area.

If you want fresh fish, this is the place as it comes directly from their own boats at Cap’t Ben’s Fish Dock right next door.

There’s nothing gourmet about Bracco’s, just good fresh food baked, steamed or fried.

Otto’s Sea Grill
Man, this is THE hangout. Bikerish, but friendly Otto’s offers indoor and outdoor dining and decent food.

The outdoor area has two bars and a very small stage for the band. There’s even a dance floor.

If you’re looking for nightlife give Otto’s a try.

E.B. Elliot’s
This is the newest entry and most upscale restaurant on the Nautical Mile dining scene.

Menu offerings range from burgers and fries to award winning steak, slow roasted prime rib and seared ahi yellow fin tuna.

You can enjoy your meal from a second story balcony with a clear view right down the canal or the large outdoor dining area. E. B. Elliot’s is a classy place and of course, not cheap.

Ice Cream & Miniature Golf

Got kids? You might want to take them to the Crow’s Nest Miniature Golf course or take them to one of the ice cream shops for some ice cream (they can’t complain about all the time you’re spending in the gift shop when they’re mouths are full).

Try: Ralph’s Italian Ices or Pip's Ice Cream Parlor.

Marinas

Men can look at boats in ways that make women jealous.

With boatyards, marinas and boat dealers (okay, yacht brokers), along the length of the canal the Nautical Mile is the perfect place to fantasize about the boat you might someday own.

Some marinas are gated, so be careful you don’t get locked in. Yes, it’s happened to me. Luckily after a short time a boat owner with a key showed up and let us out.

Fish Markets

For some people the fish markets are just ugly, smelly places, but for me they are heaven on earth.

I love looking at all the different fish spread out on the ice. I love the wet floors, the smell, the lobster tanks and the bushels full of blue claw crabs. There must be something in my blood.

If you like fresh fish, this is the place to buy it.

There are three fish markets on the Nautical Mile offering everything from catfish to snappers, bluefish and tuna, clams, cockles, crabs, lobster and oysters, mussels, squid and octopus, scallops, conch, steamers and flounders.

The list is almost endless. It’s off the boat fresh and it’s all delicious.

Live Music

Most of the eateries on the Nautical Mile have live music. It’s not hard to find, just keep your ears open and go with what you like.

More than the food it’s usually the music that draws me in to a particular place.

One Sunday afternoon while my girlfriend and I were enjoying a beer at Otto’s, I found myself standing in the way of a band ( Strung Out ) setting up their equipment.

Suzin, the band’s manager, simply informed me that since I was standing in her dancing spot, I’d have to do the dancing instead. That was the start of a snappy banter (Suzin is quite the spitfire) that went on all night long.

And, we got to meet a celebrity.

Rocco Abbondola (a.k.a. Rocky The Dancer) showed up!

Left: Rocky and Suzin take a break between sets.

What? You’ve never heard of him?
That’s okay, neither did we, but he's someone we’ll never forget.

Gift Shops

No seaside attraction would be complete without gift shops. You know, the kind where you can buy a starfish or a kite or a painting by a local artist? The Nautical Mile has a few, but my favorite is Frank's Art Shack.

The place is packed so full of stuff it's hard to walk, the prices seem reasonable and there are a lot of nice photographs and artwork for sale.

Cruises & Charter Fishing Boats

Several cruise boats and a fish load of charter and party boats hail from the Nautical Mile and Guy Lombardo Boulevard on the opposite side of Woodcleft Canal.

There are too many boats to list here, but you can go for a dinner or casino cruise or even have your wedding afloat. And, you can charter a boat for any kind of fishing you like.

Of course, for things like this it’s best to make reservations ahead of time.

Lodging

If you’re visiting Long Island and want to stay near the Nautical Mile there are two hotels in Freeport to choose from:

Freeport Motor Inn & Boatel (516-623-9100)

Yankee Clipper Motor Inn (516- 379-2005)

Getting Here & Parking

Getting to the Nautical Mile is not as hard as these directions make it seem. The route is clearly marked and all you really have to do is follow everyone else once you get off the parkway.

  1. Meadowbrook Parkway south to Merrick Road west.
  2. Left on Mill Road.
  3. Left on Henry Street (South Main Street)
  4. Right on Atlantic Avenue.
  5. Left on Guy Lombardo Boulevard
  6. Right on Front Street.
  7. Left on Woodcleft Avenue.

Once you get here start looking for a parking space. If you don't see any or don't like parking on the street, look for the municipal parking lot on your right about halfway down.

If there's nothing available there, you can park legally on the side street west of Woodcleft Avenue. Just drive through the parking lot and you'll see it.


Talk:Nautical mile/Archive 1

According to WP:UNITS, the preferred wikipedia abbreviation for nautical mile is nmi. This is to avoid confusion with nanometer, although one would think the context would be enough. I think this probably should be in the article, but am putting it here, as someone questioning it is likely to ask here. I only hesitate to put it in the article as it seems like wikipedia self references are to be avoided in mainspace. --J Clear (talk) 17:59, 2 February 2008 (UTC)

Having spent several years in the Navy, I have made some adjustments based on the following:

Nautical Miles for navigation are measured at exactly 6,000 feet (2,000 yards). A cable is 1/10 of a mile, or 200 yards. A cable also happens to be exactly 100 fathoms. While this measurement differs slightly (about 76 feet per mile) from the internaitonal standard, it is used by most navy and merchant vessels because of the much simpler mathematics involved.Mattwilkins 16:15, 18 October 2005 (UTC)

I cannot add clarification to this or a reference. I can agree with below - exactly 2000 yards to is a close approximation, simplify math. However I believe No mariners of any country use meters & kilometers at sea. Matt Wilkens defines cable and fathom as sub-units of nautical mile, I do not think that is the orginal definition of those units, instead I suspect original cable and fathom definition was perhaps as 6 feet = 1 fathom, 1 cable = 100 fathoms. Amongst mariners the 6000 feet = 1 nmi is accepted. 74.214.43.199 (talk) 01:41, 21 October 2010 (UTC) Can you add a good authoritative a reference for this? A link to some online Navy standards handbook, for example? In which country's Navy was that? Is this really an official definition, or just a crude approximation for rule-of-thumb calculations in countries that still use feet and yards? Markus Kuhn 20:28, 19 October 2005 (UTC) The Canadian Navy. The Bride Watchkeeper's Exam uses 2000 yards to the Nautical Mile. Mattwilkins 08:11, 15 November 2005 (UTC) Simpler only if you're using feet, fathoms and cables. Don't you mean "most U.S. navy and merchant vessels"? Jimp 2Nov05 Well all vessels use these measurements, as the metric system is very difficult to use to any effect. How exactly is the logical and coherent International System of Units (SI) "very difficult" to use on the sea? Or the air for that matter? Samy23 22:11, 14 January 2007 (UTC) I take it you are not a navigator. When you are working with nautical charts, it is usually easier to measure a distance using the latitude markings on either edge of the chart than to find the scale, which is frequently folded out of sight, especially on smaller craft. Also you are frequently dealing with converting degrees/minutes/seconds to distances, where the nautical mile is equivalent to 1 minute of arc (of latitude). For similar reasons, the knot is still used as the unit of velocity in the sea or air. In a way the nautical mile is similar to the hectare, both have a niche use where they are more efficient to use than SI units. --J Clear (talk) 17:49, 2 February 2008 (UTC) This is a weird sentence "Also in maritime navigation, nautical miles can be divided into 10 cables, although the present day definition of the cable uses a much more precise method.". "A tenth of a nautical mile" is perfectly precise, especially if nautical miles are defined with respect to meters which are defined with respect to the speed of light. —Preceding unsigned comment added by Schmmd (talk • contribs) One tenth nautical mile was a stadion of 185m. The Greeks measured 8 stadions (cables) to a thousand of land (mia chilioi) and 10 stadions to a nautical mile. The Romans measured 75 mille passus or milliare to a degree. 12.187.95.196 (talk) 10:30, 19 September 2013 (UTC)

"It bulges at the equator like a spinning top," says the article. Do spinning tops bulge at the equator? Jimp 2Nov05

They would. If they were made up of a sufficiently plastic material.--zumanon 14:13, 25 January 2007 (UTC)

In an edit summary, Ericg said "rv - if you think about it, bulging at the equator means the north-south distance is shorter at the equator, not longer."

The problem is, his thought experiment would lead to the opposite conclusion when it is farther away, the same angle subtends a greater distance.

The problem is, we don't normally measure geocentric latitude, so we don't have our angles located at the same origin. Instead, we normally use geodetic latitude see the article, it's too complicated to summarize here. If we used geocentric latitude, a minute of arc would be greater at the equator than at the poles.

But with the geocentric latitude we do use, a minute of arc is greater at the poles than at the equator. The numbers aren't exactly the same, however, and I haven't checked yet to see which kind of latitude the numbers used in the article correspond to. There are also a few other ways that could possibly be used to measure latitude (which is what you measure as you travel along a meridian of longitude). Gene Nygaard 00:17, 13 December 2005 (UTC)

Geodesy#Units and measures on the ellipsoid states: "A nautical mile is one minute of astronomical latitude. The radius of curvature of the ellipsoid varies with latitude, being the longest at the pole and shortest at the equator as is the nautical mile". So the statement of Nautical_mile#History: "According to WGS84 the length of one minute of arc along a meridian on the Earth's surface varies from 1852.2 m near the poles to 1855.3 m near the Equator." cannot be true. Nor does the article WGS84 support it. Bo Jacoby 13:14, 21 July 2006 (UTC)

The length of a Sea Mile is the shortest at the Equator (1842.9m) and the longest at the Poles (1861.7m). An average value of 1852.3m is at 45 degrees Latitude. (IYT YM Ocean handbook). A cable, being a tenth of a mile, equals 185.2m or ROUGHLY 200 yards. — Preceding unsigned comment added by Bingbongbelgium (talk • contribs) 20:12, 12 March 2007‎

Seeing that the sea mile is 6000 feet exactly, it can hardly vary from place to place. It must be the metre (an other geographic unit, equal to 0.1 centisimal second), that varies. A nautical mile represents a degree at the surface of a sphere approximating the earth. Wendy.krieger (talk) 07:50, 3 June 2012 (UTC)

It sounds like the sea mile is defined in different ways by different organisations (a really good reason not to use this unit). The article should start by pointing out the ambiguity, and then provide the various conflicting definitions. Dondervogel 2 (talk) 10:35, 3 June 2012 (UTC) A meter is a unit of length that does not vary anywhere on Earth's geoid. If it was oriented along the equator it would subtend 2.16 milliseconds of time. If it was oriented parallel to any other line of latitude (all small circles), it would subtend greater periods of time at greater latitudes. At 89° it would subtend about 124 ms. A nautical mile is one arcminute (not one degree) of any great circle on the surface of the Earth, including along the equator and along any meridian/antimeridian, but not along any parallel of latitude other than the equator. Using this definition it varies no more than 0.5% from 1852 meters, the International nautical mile. The "sea mile" definition of 6000 feet is due to Richard Norwood in his extraordinarily popular Seaman's Practice (1637) which was still being sold in 1776, and quoted as an authority in 1822. He personally observed the altitude of the Sun in London at the summer solstice of 1633 and in York at the summer solstice of 1635, and measured the meridional distance between them using chains and pacing. He then calculated that a degree of latitude was 367,196 English feet, but rounded this to 360,000 feet per degree or 6000 feet per arcminute. All commentators until the mid 19th century noted that 6000 feet was a rounded value. — Joe Kress (talk) 05:54, 4 June 2012 (UTC) Joe Kress says: "A nautical mile is one arcminute (not one degree) of any great circle on the surface of the Earth, including along the equator and along any meridian/antimeridian, but not along any parallel of latitude other than the equator." That's not correct. As the article makes clear, a nautical mile is not one minute of any arc, but is defined internationally as 1852 meters exactly. By the way, Richard Norwood's A Seaman's Practice is still in print today, available from Amazon. Dondervogel 2 says: "It sounds like the sea mile is defined in different ways by different organisations (a really good reason not to use this unit). The article should start by pointing out the ambiguity, and then provide the various conflicting definitions." The article is about the modern term "nautical mile", not about the disused term "sea mile", so it correctly starts out by defining the former. The latter is taken up in the second section, where it is clear that there are at least three definitions of "sea mile", two of them official, and one of which has changed since 1966. . . Jim - Jameslwoodward (talk to me • contribs) 10:53, 4 June 2012 (UTC) Jim completely ignored my statement "Using this definition it varies no more than 0.5% from 1852 meters, the International nautical mile." so I was obviously refering to the nautical mile's historical definition, which is correct. Most of my definition even appears in the lead paragraph, prefixed with "about" to account for the difference I explicitly mentioned. The article is not only about the modern term nautical mile, it is about all historical definitions as well. I see two print versions of Richard Norwood's Seaman's Practice available, from BiblioBazar and Eebo editions. Both appear to be printed versions of microfilm/microfiche editions published during the last half of the 20th century. As such they contain all defects of the microfilm/microfiche editions, including off center and cropped pages and illegible letters, words, paragraphs or pages. The second, Eebo editons, is obviously a copy of the copy in Early English Books Online viewable at many libraries (one page at a time). — Joe Kress (talk) 01:45, 5 June 2012 (UTC) We're quibbling over a very small point, and since I started it, I'll take the blame. The problem here is that many readers do not understand this subject very well -- read all of this talk page, including the claim below that a nautical mile is a minute of longitude, not latitude, and you will see what I mean. Therefore, I react when someone makes a statement that may mislead other readers -- it is absolutely correct that a nautical mile is very close to a minute of any great circle -- that is, after all, the whole point of using the special unit for navigation -- and I did note your comment that it varied by less than half a percent, but you must agree that your flat statement, without qualifiers, is not correct. As for the Norwood, certainly it's a copy of a microfilm, but it interested me that it was readily available, in stock at Amazon. Of course old sea books have long lives -- Bowditch has been continuously in print for more than 200 years. Of course, unlike Norwood, Bowditch has been revised more or less continuously over its entire life. . . Jim - Jameslwoodward (talk to me • contribs) 23:08, 5 June 2012 (UTC) Early English Books Online is the online version of four microfilm collections issued between 1938 and the present. One collection is Early English Books by Donald Wing, which contains Mr. Richard Norwood's Works, which contains the 1670 ninth edition of Seamans Practice. Although the online version has a few duplicate pages, and many pages that tilt toward each other, none of this affects its legibility. I did not consult either printed version. After observing the altitude of the Sun from both York and London and measuring the length between them in chains, Norwood concluded on page 5 that one degree of a great circle was 367196 English feet or 367200 feet "lacking 4 feet, which here we regard not." Norwood stated that the latter made a degree 69 English miles 4 furlongs 14 poles [69.54375 statute miles, where 8 furlongs/mile × 40 poles/furlong × 16.5 feet/pole = 5280 feet, which conflicts with 367200 feet / 5280 feet/mile = 69.54545 miles. Norwood mentioned "and about one half [of a pole]" earlier, but not here. He should have specified an additional 9 feet beyond 14 poles for 367200 feet (he mentioned 5 feet earlier for 367196 feet)]. On page 48 he assigned to a degree only 360000 feet so a mile was 6000 English feet. This was intentionally shorter than the length of the degree that Norwood measured so that reckoning by a log line with knots would indicate that the ship had sailed its intended distance before it reached its intended destination to avoid surprise, and "for the rotundity of the number". Norwood never used the terms "sea mile", "geographical mile", or "nautical mile". He only used "mile" for each of the 60 miles in a degree. — Joe Kress (talk) 05:10, 23 June 2012 (UTC)

In the discussion on the Knot (speed) page, someone says regarding the metric conversion to km: "1.852 is a round up (the actual precise number being 1.851999985024)" Anyone? Fizzybrain 12:38, 17 April 2006 (UTC)

I just looked at the BIPM reference. It says 1852 not 1852.5 meters. Has our definition really been wrong all along? I just corrected it. 16:09, 13 December 2006 (UTC)

I modified the conversion section to indicate which conversions have exact (rational) values, and also grouped the two approximate values together at the end. Lacking any more precise definition of geographical mile than one arc minute at the Earth's equator, this can only be as exact as the current estimate of the latter, and likewise for the arc minute itself, which certainly is not exactly one nautical mile given the SI standardization to 1852 m. --Vaughan Pratt 01:02, 15 August 2007 (UTC)

In one section ( toward the bottom ) the Wiki page lists a nautical mile as exactly 1,852 meters. In another section, we're told "The Imperial (UK) nautical mile, also known as the Admiralty mile, was defined in terms of the knot such that one nautical mile was exactly 6080 feet (1853.184 m):[5] it was abandoned in 1970[5] and, for legal purposes, is now converted to metres on the basis of one UK nautical mile = 1853 metres exactly.[6]" —Preceding unsigned comment added by 70.91.201.209 (talk) 23:26, 15 January 2010 (UTC)

Both are correct. The international nautical mile is exactly 1,852 m. The Imperial nautical mile was defined as 6080 feet, which is equivalent to 1853.184 m. However, when the UK decided to abandon the Imperial nautical mile, they also decided that if old references to it need to be converted to SI, the old references should be converted with a conversion factor of 1853 meters to the Imperial nautical mile. --Jc3s5h (talk) 23:50, 15 January 2010 (UTC)

This entry never explains what SI is -- perhaps whoever added it could include it? It's not very clear to me what SI is from the context.

International System of Units, now Wikilinked in the second sentence. Atlant 16:58, 5 June 2006 (UTC)

In the article box where it has conversions is states 1 nautical mile = 1088.259 miles, which can't possibly be right. However, I know nothing about nautical stuff so is there something I'm missing here? --Cammy 19:15, 11 August 2006 (UTC)

Somebody has screwed up the <> template. Atlant 00:02, 13 August 2006 (UTC)

"The term 'knot' derived from the practice of using a knotted rope as a method of gauging speed of a ship. The rope would be thrown into the water and the rope trailed behind the ship. The number of knots that passed off the ship and into the water in a given time would determine the speed in 'knots'."

This really sounds like nonsense folk etymology. I'd always had the impression 'knot' was simply a respelling of 'nauts', short for 'nautical miles (per hour)'. This thing about dropping knots sounds like nonsense. 192.128.167.68 11:00, 25 August 2006 (UTC)

Nope, that's the exact etymology. So many knots on so many seconds. Atlant 18:20, 27 August 2006 (UTC) It's correct. The only early way to know a ship's speed was to use what is called a log line. Check dictionary definition 10b. ericg ✈ 19:01, 27 August 2006 (UTC) Sorry, I've never included a cite before. If someone else doesn't mind doing it this is an excellent explanation of the nautical term "knot." It even explains that "naut" as in nautical and "knot" as in a marker in a rope is purely coincidental. The use of a wooden wedge is explained, to serve as a sea anchor, thus insuring that the rope would play out properly, along with a 30 second "hourglass", and a length of knotted (not nauted) rope. The process involved three persons. The timekeepr, the knot counter, and the rope player-outer.

This link http://www.tallshipbounty.org/Demos_ChipLog.html includes photos and further explaination of the "chip log."

It all started with logs being thrown overboard over the bow of a ship on a mark and someone counting the seconds that passed until the log passed the stern. The vessel's size was known and this way the speed could be calculated and entered in the LOG-book. Later they tied a rope to the log so they could re-use the same log over and over again and thus saving valuable storage space. Eventually they ended up with the knotted rope.

The articles states that 1 nautical mile is equal to 1.1507794 geographical mile. Yet, the geographical mile article states that geographical mile is 1855 meters, which means that 1 nautical mile is equal to 1852/1855 = 0.9984 geographical mile. Hence, (at least) one of the two statements has to be wrong, though I do not know which one.
--158.38.82.84 12:50, 12 January 2007 (UTC)

Changed, I assume that one nautical mile is equal to 0,9984 geographical mile (according to the [Geographical mile] definition). Tatrgel 13:52, 14 January 2007 (UTC) The quick-and-dirty approximation used for practical navigation is that a nautical mile is 15% longer than a statute mile: 5280 ft X 1.15 = 6072 ft ≈ 6,076.1 This is also known as "slide rule accuracy" — the kind of precision one would get with a traditional E6B Flight Computer. —Quicksilver T @ 19:11, 8 January 2009 (UTC)

I have almost by chance noticed that the radius at the poles were shown to be greater than the radius at the equator, which is of course wrong it is a known fact that the earth is bulging at the equator. Also the corresponding lengths of one minute of arc was wrong. So I consulted the WGS 84 for the radii and made the necessary calculations of the arc myself. --zumanon 14:05, 25 January 2007 (UTC)

Actually I have seen the same error in various websites from which I suppose the main body of the article has been copied. If I have time I will revisit this article and check other figures at least for conceptual errors.--zumanon 14:10, 25 January 2007 (UTC)

No error, the radius of curvature of a meridian attains its minimum at the equator and maximum at the poles. You are probably thinking of another radius, namely the distance from the surface to the center of the earth, which as you say is the other way round. Take a look at the geodetic constants in http://www.jqjacobs.net/astro/xls/aegeo.xls. The relevant ones here are sma (semimajor axis or equatorial radius), smi (semiminor axis or polar radius), fr (flattening reciprocal, = smi/sma), and rcp (radius of curvature, polar), all IUGG values (for consistency). Missing is rce (radius of curvature, equatorial). You can get all of these from just sma (6378137 exactly) and fr (0.996647189318820) alone, using smi = sma×fr, rcp = sma/fr, and rce = sma×fr 2 . So smi and rcp go in opposite directions from sma, while rce/rcp, the ratio of the two curvatures, is fr 3 = .989975, i.e. the radius of curvature decreases by 1.0025 per cent going from pole to equator. Memorizing this as one percent is all the accuracy you'll ever need in practice (oblateness works in mysterious ways). --Vaughan Pratt 22:33, 16 August 2007 (UTC)

Right now the content related to the various articles relating to measurement seems to be rather indifferently handled. This is not good, because at least 45 or so are of a great deal of importance to Wikipedia, and are even regarded as Vital articles. On that basis, I am proposing a new project at Wikipedia:WikiProject Council/Proposals#Measurement to work with these articles, and the others that relate to the concepts of measurement. Any and all input in the proposed project, including indications of willingness to contribute to its work, would be greatly appreciated. Thank you for your attention. John Carter 20:56, 2 May 2007 (UTC)

Anonymous editor 74.161.41.234 keeps changing the definition to:

Unit of distance used in navigation, an internationally agreed standard (since 1959) equaling the average length of one minute of arc on a great circle of the Earth, or 1,852 m/6,076 ft. Refer to: http://geodesy.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf

However, the cited reference does not mention "one minute of arc" and it gives a much more precise length than 6,076 ft. The first is already mentioned in the 'definition' as an approximation and the second is given almost as precisely as that in his ref in a list below the definition (Conversions to other units). — Joe Kress 22:45, 27 August 2007 (UTC)

The anonymous editor is also wrong that it became an international standard in 1959. Various sites, including the BIH site, state that it was internationally accepted in 1928. 1959 is the much later year that the United States accepted it. I left a note on his talk page (User talk:74.161.41.234) requesting him to respond here. Because all of his edits have used the same numeric IP address, he should see an alert that he has a message on any Wikipedia page. — Joe Kress 23:50, 28 August 2007 (UTC) There should be a short and absolute definition in the beginning of the main article text of that what a nautical mile equals to meters. This is the main inadequacy of the article.It must be clearly expressed that a nautical mile e quals to 1852 m. at the very begining. because many people may want to obtain shortly the meter equivalent of nmi.so i am writing down this knowledge at the main definition paragraph .yes it is existing in the frame but it must also be in text either. —Preceding unsigned comment added by 85.108.76.2 (talk) 03:02, 12 February 2010 (UTC)

I reformatted the reference in the lead sentence to point directly to Table 8 in the BIPM brochure, rather than a section that contains several tables. I also removed some unsourced remarks from the footnote. In particular, the footnote contained the quotation "expected to continue to be used for many years", but that phrase does not occur anywhere in the BIPM brochure (unless there is some quirk that prevents the search facility in Adobe Acrobat Reader from finding it). --Gerry Ashton 18:01, 30 August 2007 (UTC)

Sorry for the misquote. The phrase is actually, "continue to be used for many years", which occurs in the first paragraph of section 4.1: "Tables 8 and 9 contain units that have exactly defined values in terms of SI units, and are used in particular circumstances to satisfy the needs of commercial, legal, or specialized scientific interests. It is likely that these units will continue to be used for many years." This quote is also the source for the excised statement that it is "an exact SI definition". I've not been able to confirm the original statement that "At one time, the nautical mile was discouraged for use by the BIPM" due to a lack of access to early editions of the SI brochure. The 7th edition notes that in 1969 the CIPM "listed three categories of non-SI units: units to be maintained to be tolerated temporarily and to be avoided", but fails to state which category contained the nautical mile. An early table containing the nautical mile from an unknown edition was entitled "other units outside the SI that are currently accepted for use with the SI, subject to further review". The table in the 6th edition (1991) is entitled "units temporarily accepted for use with the SI" while the table in the 7th edition (1998) is entitled "other non-SI units currently accepted for use with the International System" (but its "use is not encouraged"), compared to the 8th edition (2006), which only has "other non-SI units". Although section 4.1 is entitled "non-SI units accepted for use with the SI, and units based on fundamental constants", even the preface to table 7 states that its units "are not generally used with SI". — Joe Kress 05:56, 1 September 2007 (UTC)

If you have a view on what abbreviation(s) should or should not be used, you may be interested in reading this discussion. Thunderbird2 20:55, 4 September 2007 (UTC)

As it stands now the lead mentions the abbreviations M, NM and nmi, and the Unit Symbol section mentions M and nm. I think the Unit Symbol section should mention NM and nmi as well. The discussion mentioned above has been archived. Ulflund (talk) 11:47, 8 December 2011 (UTC)

In the history section, the fourth paragraph begins: "Other nations had different definitions of the nautical mile." I infer from this phrase that the preceding three paragraphs have been refering to one or more specific nations, yet none is mentioned. --Jamestowell 19:27, 9 September 2007 (UTC)

You're right. It doesn't make sense. Feel free to improve the wording yourself when you spot something like this. Thunderbird2 19:49, 9 September 2007 (UTC)

I have simplified the passage that explains the length of a minute of latitude. Since nautical miles are ordinarily used in navigation, it is appropriate to round to the nearest meter. Also, since nautical charts use geodetic latitude rather than geocentric latitude, I removed the passage about geocentric latitude.

Also, I added a reference to the Explanatory supplement to the Astronomical almanac. --Gerry Ashton (talk) 19:59, 6 February 2008 (UTC)

When was it adopted? Septentrionalis PMAnderson 16:09, 3 March 2008 (UTC)

N.A.M. Rodgers, in The Wooden World: An Anatomy of the Georgian Navy, makes the following statement, "Commodore Frankland. reported dangerous variations in marking the log line, and consequently in reckoning distance run: 'The Winchester, by allowing only forty-two feet to a glass of thirty seconds, overrun her reckoning by near a hundred leagues between Madeira and this island [Barbados]. 35 He asked for an Admiralty order fixing the length of the log line. Endnote 35, Public Records Office, Letters of the Admiralty, T. Frankland, 18 Nov 1755. Now the above is far from a statement that in 1755, as a consequence of variations in marking the log line, the Admiralty fixed the nautical mile. However, as this period saw an increased cognizance in the import of precise and reliable navigation, I believe we are getting close, if you will. Would anyone care to opine? --Crusher1 (talk) 03:33, 20 April 2008 (UTC)

Circular Definition

The knot article defines a knot as one nautical mile per hour. The nautical mile definition says a nautical mile is defined as one knot divided by one hour. Somewhere there has to be an original definition for the (admiralty) nautical mile, but what was it? Rhialto (talk) 08:56, 7 March 2011 (UTC)

The article title is "Nautical Mile so", and the page for "Nautical Mile" redirects here, but nowhere in the article is the "so" part defined. What does it mean? 150.101.166.15 (talk) 23:41, 27 March 2008 (UTC)

The page has been vandalised, but I don't know how to fix it. The "so" is someone's idea of a joke. Does anyone know how to retrieve the correct name please? Thunderbird2 (talk) 10:14, 28 March 2008 (UTC) I have reported this vandalism WP:AIV. I hope an administrator will know the best method to undo this problem. --Gerry Ashton (talk) 14:20, 28 March 2008 (UTC) User:Skomorokh has fixed the problem. --Gerry Ashton (talk) 14:50, 28 March 2008 (UTC) Thanks. Thunderbird2 (talk) 15:36, 28 March 2008 (UTC)

The Admiralty Manual of Navigation and the RYA Navigation Handbook both make a helpful distinction between these two terms. A Sea mile is the length of one minute of arc, along a meridian. It is actually calculated as the angle between two intersecting normals, it does not make reference to the centre of the earth. A "normal" is a line at right angles to a tangent and running through the tangent at the point it touches the curve. Since the earth is not a sphere, and its cross section not a circle, then the length of a Sea Mile does alter according the latitude it is taken. When a navigator takes a distance measure from the vertical edge of a chart, he is measuring sea miles.

Nautical Miles are an attempt to create a "standard" or average Sea Mile, one which is the same no matter the latitude it is used. This is vital for specifying speeds, unless a knot is to have a slightly differing value at different latitudes. This is largely a matter of agreement between various maritime authorities.

To sum up, this excellent article would be improved still further if the diagram were to be changed to say "sea miles", and distinction between the two be made more clearly.

The variation of the length of a degree of latitude (60 minutes) relative to an ellipsoid is discussed at Latitude#Degree length. — Joe Kress (talk) 02:46, 12 April 2008 (UTC) Good point. That's something I noticed a while ago, then completely forgot to do anything about. When I find my copy of the Mariner's Handbook, I'll have a go at properly defining sea miles. There will probably have to be a mention made on Mile as well, and a redirect page created for Sea mile. Wardog (talk) 15:34, 18 June 2008 (UTC) I find the definition of sea mile in this article confusing. When I went to the source (The Admiralty Manual of Navigation) I was not confused. I made an ill-advised edit, which I have now reverted. It's the apparent (but not actual) redundancy of "1' of arc of latitude . along the current meridian" that throws me off track. OK. This is looking more and more like a problem with the way my brain is wired, and less and less like a problem with the writing. But for me, I think I could understand it better if the first bit just said 1' of arc along the current meridian at the current latitude. Then a second sentence could state this corresponds to 1' of latitude and briefly explain why 1' of latitude varies as a function of current latitude. In the source, when it was separated out, I found it easier to follow. Does anyone object to my trying to do a small rewrite in the next few days? Susfele (talk) 17:06, 20 June 2010 (UTC) Thank you, Jameslwoodward, for rewriting the sea mile definition. It's both more succinct and more understandable. Susfele (talk) 00:31, 22 June 2010 (UTC)

The Mariner's Handbook defines the International Nautical mile as 1852m and the Sea mile as "the length of one minute of arc measured along the meridian in the latitude of the position its length varies both with the latitude and with the dimensions of the spheroid in use". It defines the geographical mile as "the length of one minute of arc measured along the equator its value is determined by the dimensions of the spheroid in use".

The Admiralty Manual of Navigation Vol 1 (1987) says that the abbreviation for a nautical mile is "n.mile". It gives the abbreviation for sea mile as "M" on charts and '(as used for minutes of arc) elsewhere.

Tim Bartlett —Preceding unsigned comment added by 82.153.197.217 (talk) 12:50, 2 January 2009 (UTC)

I'm surprised to see 'radar mile' here. I think it is in the wrong article.

The point is, a radar mile is measurement of time, not a measurement of distance. As stated it is the time it takes for a radar (RF) signal to go a mile, strike an object and be reflected back to its origin. A radar mile is therefore 12.36 micro-seconds.

It's a bit like calling 100 'sprint' metres, 20 seconds. (the time to run 100M and run back again) I'm being picky but it there is no other connections this could be deleted This information only belongs in the Radar article (or maybe in the Mile article —Preceding unsigned comment added by 220.101.28.25 (talk) 01:01, 25 October 2009 (UTC)

The radar mile is a unit of time that it takes radar to travel one mile. This is the time it takes radio waves to go out and back, one mile. It is a unit of time, but as 'knot' is here as a derived unit (nm/hr), so should this unit (nm/radar). --Wendy.krieger (talk) 07:10, 30 August 2010 (UTC)

It states "The nautical mile (symbol M, NM, Nm or nmi) is a unit of length corresponding approximately to one minute of arc of 'latitude' along any meridian. By international agreement it is exactly 1,852 metres (approximately 6,076 feet).”

However, it is not latitude, but longitude that one measures a nautical mile from (on a chart), as the length (or distance apart) of the minutes of latitude vary depending on how far from the equator one gets, whereas minutes of longitude do not. Hence, a nautical mile measured from a line of latitude near the Pole would give you a much shorter nautical mile than if measured along a line of latitude at the equator. However this variation does not occur in the lines of longitude and hence why longitude is ALWAYS used to measure a nautical mile.

So that first line, and any others of similar nature referring to ‘latitude’ as the measure of a nautical mile in the article needs to be changed. — Preceding unsigned comment added by 124.150.97.91 (talk • contribs) 23:31, 15 February 2011

  • Apologies Cinderella157, I'd never thought of that way of getting around the loathsome diff engine before! I don't mind reverting and making the changes again one at a time if that helps? ‑‑ YodinT 14:28, 10 November 2015 (UTC)

Nautical Mile: If a nautical mile is greater at the poles than at the equator, how can the earth be considered an oblate spheroid rather than a prolate spheroid? How can it be said that we know the earth is wider at the equator than at the poles given the length of a nautical mile is longer at the poles than at the equator?Goodhayman (talk) 12:33, 14 April 2011 (UTC)

A frequent source of confusion. What you need to do is think about what latitude is. Suppose the Earth were much more oblate-- still an elliptical cross-section, but pancake-shaped. Where would 45 degrees latitude be? Near the equator, or near the poles? Tim Zukas (talk) 16:26, 21 October 2011 (UTC) Also the elliptic shape of Earth is a few meters of difference, or so - crossing waves at the oceans or sailing where the tides are strong means more. Not to speak of mountains on land. Boeing720 (talk) 02:53, 16 January 2015 (UTC)

Unless there is an objection, I am going to remove this section. I can't find any substantive reference for a "telegraph mile" or "telegraphic mile" except a few sites on Google that provide conversions into or out of it. They may simply be built off of the definition here. It is certainly of less importance than many other uses of "mile" that we do not include here. . . Jim - Jameslwoodward (talk to me • contribs) 13:01, 17 February 2012 (UTC)

There being no objection after waiting 2+ weeks, I have removed this section. . . Jim - Jameslwoodward (talk to me • contribs) 14:24, 7 March 2012 (UTC)

From a mathematical point of view are the zeros incorrect. They suggest an accuracy of six digits. But the true value (modern definition) is 1,852 meter exactly. It's an integer value, not a floating one or "with decimals". There is no call for adding the zeros. Actually 1,852.00 means a value somewhere between 1,851.995 and 1,852.004. On the other hand in order to point out this is a four digit integer, it's expressed 1.853 x 10 3 , but that is an exaggeration. But not the added zeros. And I'm not a mathematican, just someone that has studied mathematics to a cetrain level (some lower university courses) a long time ago. Boeing720 (talk) 02:45, 16 January 2015 (UTC)

A: Read this and draw your own conclusions. Dondervogel 2 (talk) 09:22, 28 December 2015 (UTC)

That page simply shows the futility of trying to explain earth-centric nautical miles in SI metric or imperial units! For example, is a nautical mile on the moon equal to 1852m? Santamoly (talk) 09:31, 4 March 2016 (UTC) One nautical mile is equal to 1852 m, by definition. It doesn't matter whether you are on Earth, Mars or Alpha Centauri. But that's not what this thread was about. Dondervogel 2 (talk) 17:05, 4 March 2016 (UTC)