Physics/Nautical Mile

posted by .

My previous posts have dramatically improved my understanding of how a NM is derived but other questions have been raised:

In most books entitled "Pass your Day Skipper" or "Yachtmaster" or similar nautical/navigational publications Latitude is described and illustrated as the angular distance 0 degrees to 90 degrees either N or S of the equator and in the illustrations the angles are drawn using a common centre of the earth. Is it fair to assume this is an appropriate simplification of the more complex reality.

I am having difficulty assimilating what used to be my understanding ie. the simplified version and my new understanding the more complex version.

OR am I just becoming more confused?

Mike

  • Physics/Nautical Mile -

    Those drawings are simplified. The only reason that the "new" definition of the minute of latitude being arc disance subtended by one minute from the center of curvature is that satellite mapping has made it possible to accurately map the real Earth Surface. For surface navigation, one common center of the Earth is possible. Few folks navigating are at the S or N pole, and those who do use GPS.

  • Physics/Nautical Mile -

    Hello again Bob, Thanks for your reply. The point that has grabbed my attention now is you refer to the "NEW" definition of the minute of latitude. Things are slowly falling into place at this end. Do you happen to know when the "NEW" definition of latitude was introduced?

    Mike

  • Physics/Nautical Mile -

    It couln't be done until we knew the shape of the Earth with some precision, in particular the semimajor and semiminor axis. WGS 84 is the system that defined these lengths with some precision. With that, the point of curvature could be determined, and thence the distance subtended.
    http://en.wikipedia.org/wiki/WGS84
    By the way, the international standard for a nautical mile is fixed as the average distance. All this is somewhat like mom's favorite apple pie recipe, it depends on who is eating, when, and what ingredients were available at cooking.

  • Physics/Nautical Mile -

    Hello Bob, love your analogy about mom's apple pie recipe.

    Allow me to enter the NM debate at this point.
    Do you happen to have a good explanation re the origin of the k in knots for "nautical miles per hour"?

  • Physics/Nautical Mile -

    http://mathforum.org/kb/message.jspa?messageID=1470195&tstart=0

    This is as I learned it many years ago as a seaman.

  • Physics/Nautical Mile -

    That makes sense.
    BTW, interesting thread.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Physics/English/Nautical Mile

    In my previous posts about the NM I think part of my problem is I do not understand the meaning of the word "SUBTENDED". Explanation please. Mike
  2. Physics/Nautical Mile

    Still studying! I have The Macmillan & Silk Cut Nautical Almanac from 1981 which pre-dates WGS84 and they make reference to the NM being 6046 feet at the equator and 6108 feet at the poles. Conversions to metres = 1842.82m and 1861.71m. …
  3. Precalculus

    A nautical mile equals the length of arc subtended by a central angle of 1 minute on a great circle on the surface of Earth. If the radius of Earth is taken as 3960 miles, express 1 nautical mile in terms of ordinary, or statute, miles.
  4. Calc

    Two commercial airplanes are flying at an altitude of 40,000 ft along straight-line courses that intersect at right angles. Plane A is approaching the intersection point at a speed of 427 knots (nautical miles per hour; a nautical …
  5. Calc

    Two commercial airplanes are flying at an altitude of 40,000 ft along straight-line courses that intersect at right angles. Plane A is approaching the intersection point at a speed of 427 knots (nautical miles per hour; a nautical …
  6. math

    The distance between two points is correctly expressed as 720 statute miles or 630 nautical miles. Which of the following most closely approximates the value of one statute mile in terms of nautical miles?
  7. math

    A ship sails due north from a position 5 degrees, 28' South Latitude to position 6 degrees, 43' North Latitude. Given that one minute of latitude is equivalent to 1 nautical mile, the ship has sailed a distance of A. 75 nautical miles …
  8. physics

    The depth of the ocean is sometimes measured in fathoms (1 fathom = 6 feet). Distance on the surface of the ocean is sometimes measured in nautical miles (1 nautical mile = 6076 feet). The water beneath a surface rectangle 3.70 nautical …
  9. physics

    The depth of the ocean is sometimes measured in fathoms (1 fathom = 6 feet). Distance on the surface of the ocean is sometimes measured in nautical miles (1 nautical mile = 6076 feet). The water beneath a surface rectangle 3.70 nautical …
  10. Simple Geography

    The provisions of the United Nations Conference of the Law of the Sea (UNCLOS) give coastal countries navigational and economic sovereignty over which of the following zones?

More Similar Questions