Re: [Paddlewise] Latitude distances

Dave Williams wrote:

> Hey all,
>
> I have a question that there may not be a definative answer to.  OK, 1
> degree of latitude equals 60 nautical miles right?  And, there are 360
> degrees in a circle right?  How can there be 360 degrees of 60 nautical
> miles each (degree) at both the equator and at latitude 60?  The circle, of
> course, is much much smaller at the 60 degree latitude.
>
> What's going on here?
>
> Cheers,
> Dave
>
> Dave Williams, SeaCanoe Training Director
> Home tel: +66 76 254-514
> Work tel: +66 76 212-252
> Fax: +66 76 212-172
> dave_at_seacanoe.com
>
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Dave,

I think the confusion comes from the difference between latitude and longitude.
The meridians of longitude all pass through two points: the North and South
poles. Along each meridian, one degree of  LATITUDE = 60 nm. Between meridians,
say 90 W and 91 W, one degree of LONGITUDE = 1 nm at the equator only, because
as the latitude (distance from the equator) increases, the meridians converge,
so that at the poles, they pass through a point.

Mathematically, 1 degree of longitude = cos (latitude), so that:

at lat 45, 1 degree of longitude = .707 nm

at lat 60, 1 degree of longitude = .5nm

and so on.

Hope this helps,

Roger


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