[time-nuts] FW: IIMorrow GPS units non-functional since Sunday

[Arnold Tibus]

On Wed, 20 Aug 2008 16:24:31 +1000, Jim Palfreyman wrote:

>Wow.

>Don't tell me people still use miles? Nautical or otherwise?

>What's wrong with the good old kilometre?

>Jim


Jim, 
it is quite easy to give an answer to your question:

Even using GPS geographic coordinates are still (and will be 
in future) in use, because the earth is a globe (even a bit 
deformed like a potato but is not a flat surface like a disk ;-) ! ) 
with a circumference of roughly 40000 km divided in 
360° or 21600 (arc)min = 21600 nautical miles (NM or nmi). 

Nautical charts are divided in degrees and minutes by a grid 
of intersecting lines thus allowing very easy and quick to 
measure distances positions and passages just applying a 
nautical divider (attn.: to me adjusted o n l y  on the right or left 
side of the chart, the meridians N or S value!)

To avoid nm (nanometers) with nautical miles:
The preferred abbreviation of the IEEE is nmi
For aviation use, the preferred abbreviation of the ICAO is NM

A nmi = 0.9998834 mean meridian arc minutes 
= mean historical nautical miles (approx.)
In 1929 when the International Extraordinary Hydrographic 
Conference held in Monaco was adopted a definition of 
one (1) international nautical mile as being equal to 1,852 m 
exactly.

more eg.:
http://en.wikipedia.org/wiki/Nautical_mile
http://encyclopedia.farlex.com/nautical+mile
http://citadelnavy.files.wordpress.com/2008/02/02-terrestrial-coord-sys-charts.ppt

I think even in 'modern' times  the use of nmi will therefore 
not disappear!

regards
Arnold