How Many Feet Is A Nautical Mile – This article is about the measurement of ocean speed. For the measurement of distance over land, see mile. For the US unit based on the equator, see geographic mile.
A nautical mile is a unit of lgth used for air, sea and space navigation and for the definition of territorial waters.
How Many Feet Is A Nautical Mile
Historically it was defined as the meridian arc lgth corresponding to one minute (1/60 of a degree) of latitude. Today the international nautical mile is defined as exactly 1,852 meters (6,076 ft; 1.151 mi).
One Nautical Mile Is 6080 Ft. The Same In Kilometre Is?
The word mile comes from the Latin phrase for a thousand paces: mille passus. Sailing at sea is done by sight
By about 1500 navigational instruments were developed and cartographers began to use a coordinate system with parallels of latitude and meridians of longitude.
By the end of the 16th century, Gliss scientists knew that the ratio of oceanic distances on any great circle (such as the equator, or any meridian) was constant, assuming that the Earth was a globe. Robert Hughes wrote in 1594 that the distance on a great circle was 60 miles per degree, i.e. nautical miles per minute.
Since the Earth is not a perfect sphere but a hollow globe with a slightly flattened pole, there is no constant moment of latitude, but about 1,861 meters at the poles and 1,843 meters at the equator.
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France and other metric countries say that a nautical mile is in principle one arcminute of a meridian at 45° latitude, but this is a modern justification for a cruder calculation developed much earlier. In the mid-19th century, France defined a nautical mile through the original 1791 definition of the metre, one millionth of a meridian quarter.
So the metric length for a nautical mile is 10,000,000 m / 90 × 60 = 1,851.85 m ≈ 1,852 m. France legalized the French Navy in 1906, and many metric countries voted to approve it for international use at the 1929 International Hydrographic Conference.
Both the United States and the United Kingdom used a mean arcminute—specifically, one minute of arc of a great circle on a sphere with the same surface area as the Clark 1866 ellipsoid.
The resulting arcminute is 1,853.2480 meters (6,080.210 ft). The United States chose five significant figures for its nautical mile, 6,080.2 feet, and the United Kingdom chose four significant figures for its nautical mile, 6,080 feet.
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The international nautical mile was defined as 1,852 vertical meters by the First International Hydrographic Conference in Monaco in 1929.
The meter was originally defined as 1 ⁄10,000,000 of the lgth of the meridian arc from the North Pole to the equator,
So one kilometer of distance corresponds to one centimeter (also known as centimeter of arc) of latitude. So the circumference of the Earth is about 40,000 km. Equatorial circumference slightly longer than polar circumference – measurement based on (
1/60 the latitude of Mars, a Martian nautical mile is equal to 983 meters (1,075 yd). This is very useful for celestial navigation on human missions to the planet, both as an overview and as a quick way to determine position.” Ocean Surf Zone: A different fish cage than Montrose Beach | main | Day of the New Years Chicago River Paddle: 25th Year »
What Is A Nautical Mile?
It is often good to know the distance to some kayak, destination or object. The human visual system is very bad at this job. I can easily recall many instances of pedaling for hours on end with no gain on large distant targets. It always feels like progress should be faster…
Kayaking books such as Burch or Ferrero provide some help. They provide a simple formula for calculating the distance at which objects can be seen at a given height above sea level. The range of visibility in miles is equal to the square root of the altitude measured in feet. For example, a lighthouse 100 feet above sea level will be visible from 10 miles away. The formula is for an observer at sea level.
In a kayak, you are not at sea level. For an observer in the cockpit of a kayak, you can add 1.5 miles to the range of visibility of an object derived from the formula. Half a mile is the square root of the height of eye level above the surface of the water. On average, the paddler’s eyes are only two feet above the surface. Here are some immediate applications – if you can see the feet of beachgoers as they walk near the water, you are about 2 miles from shore. It is 1.5 plus a little more for the height of the beach. Two kayaks will lose sight of each other when they are separated by three miles – one and a half miles of visibility in either direction.
This is where I was struck. The range of visibility formula is supposed to dictate you, not nautical miles. Burch, then, suggests that the range of visibility determined in this way is underestimated by about 15%. This means that the estimate of 10 miles for an object with a height of 100′ should be 11.5 miles. Interestingly, it should be the distance in nautical miles. So what’s going on here? How close is the square root estimate?
It’s time to ditch the high school trigonometry books. First, we find the mathematical solution to the problem. Then, we will have a basis for determining whether there are statutory or maritime visibility limits and how precise they are
The general shape of the earth is basically a sphere. For our purposes, the field can be reduced to a circle. The average radius from the center to the surface is about 3,440 nautical miles or 3,959 statute miles.
Any line that touches the outside of the circle can be used to indicate the range of visibility – objects above the elevation line will be visible, those below will be hidden by the horizon. Another line can be drawn from where the line of sight touches the center of the ground outside the circle. This line will have two known characteristics: (1) its length will be the radius of the Earth and (2) its angle with the line of sight will be 90 degrees. The Earth’s radius and line of sight can be seen as two sides of a right triangle. The hypotenuse of this triangle is equal to the radius of the earth and the height of the object above sea level. What we have here is a simple case of the Pythagorean theorem with two known sides of a right triangle. We may solve for unknown third parties. In our case,
By filling in the numbers and plotting the results of this equation we get the following picture. If the result of the square root solution is read in nautical miles, it will reduce the actual speed by 6%. In statutory miles, the distance is calculated to be less than 18%.
How Are Nautical Miles Measured?
There it is as clear as day: mathematically, the square root of the altitude (measured in feet) is much closer to geographical visibility expressed at sea than statutory miles.
Why, then, is the formula presented as a solution proposal in statutory miles? I don’t know the answer…
Here are some ideas. The mathematical solution gives the distance at which the top of the object reaches the line of sight. So the question is can you see the top as soon as you get to the line? For me, it depends. If the object is a mountain top, it might be “no!” It is necessary to climb above the front line of the hill to see at least a little. A mountain 400 feet above sea level reaches the line of sight when the distance is 21.3 nautical miles or 24.5 statute miles. The square root formula tells you that when you see the top of the first mountain, you are 20 miles away. According to the numbers, when you are actually 20 nautical miles away, the mountain is 47 feet above the line of sight. When you are 20 miles away, the mountain will expand by 133. When will you see the top of the mountain? I don’t know but, personally, I’d rather be closer than I think I am. To me, the definition of the sea mile seems more conservative and appropriate.
If you’re paddling at night and it’s light you’re looking for, you’ll see the light well before you reach the theoretical line. The moment when true light emerges from below the horizon will be determined more precisely than in previous scenes. Again, if the height of the light is known, its square root is best described as the distance in nautical miles, not the law. This article requires additional citations for verification. Please help improve this article by citing reliable sources. May contain unsourced material
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