[amsat-bb] Re: Grid Square..Physical Size??

laura halliday marsgal42 at hotmail.com
Sun Jul 1 18:05:32 PDT 2007


Frank A Cahoy <k0blt at juno.com> asked

>A friend and I were discussing the actual physical size of a grid square
>in kilometers and or miles and we cannot come up with anything positive.
>Can anyone reading this provide us with those actual numbers?
>No real argument involved.  Just a matter of curiosity.....
>Thank you in advance...

1 degree of latitude = 60 minutes = 60 nautical miles (by definition)

1 nautical mile = 1.852 kilometers (by definition)

1 degree of latitude = 60 * 1.852 = 111.12 km

1 degree of longitude = 60 * 1.852 * cos(latitude) kilometers

At the equator, a grid square is approximately 222 by 111
kilometers.

At 60 degrees north a grid square is approximately square,
because cos(60) = 0.5

If you want to bore people at parties, geometry on a
sphere, with great circles for lines, is an example of a
Riemannian geometry, where (among other things) the
sum of the angles in a triangle always exceeds 180
degrees.

Laura Halliday VE7LDH     "Que les nuages soient notre
Grid: CN89mg                       pied a terre..."
ICBM: 49 16.05 N 122 56.92 W     - Hospital/Shafte

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