Don White wrote:
krj wrote:

Peter Bennett wrote:

On Fri, 01 Dec 2006 14:12:52 GMT, keith_nuttle
wrote:


Since the nautical mile is defined as one minute of latitude, I
doubt it will ever disappear in earth based navigation.




The Nautical Mile was originally based on a minute of latitude, but
the length of a minute of latitude varies with latitude, so an
International Nautical Mile is now defined as 1852 metres exactly, or
6076.11549 US feet, approximately, according to Bowditch.



I believe that the nautical mile is based on the minute of LONGITUDE
not latitude. Longitude doesn't vary with changes in latitude (or
attitude). That's why when you are using paper charts (remember those)
you measure the distance with your dividers on the longitude scale on
the east or west side of the chart.
krj


Agree.. that's what they taught us in the Power & Sail Squadron courses.

ooops...I'd better dig out those old textbooks & review.
Of course, that scale we measure on the left & right sides of the chart
are the latitude scales.