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[aprssig] A math problem concerning Lat and Long

Curt Mills archer at eskimo.com
Wed Oct 6 04:33:24 UTC 2004


On Tue, 5 Oct 2004, Wes Johnston wrote:

> For close in distances, I count 1 degree north-south as 69statute
> miles.... of course one degree east-west is subject to the COS of the
> latitude.  Entirely as a quick approximation, I average the two lat's
> and use that average in my COS(lat) x 69 miles x X number of degrees.
>  From there, it's Pythagorean Theorem.... z^2=x^2+y^2
>
> Again, this is only for a close in approx... I have checked this method
> and it's good to <0.1 mile at 100 miles, which was good enough for me.

Of course the absolute easiest way of computing distances like this
is to switch to UTM coordinates.  Then everything is in meters, and
the theorem above works great...  Until you get near the edge of a
zone and have to cross zone boundaries that is.  Usually a non-issue
though.

-- 
Curt, WE7U.				archer at eskimo dot com
http://www.eskimo.com/~archer
  Lotto:  A tax on people who are bad at math. - unknown
Windows:  Microsoft's tax on computer illiterates. - WE7U.
The world DOES revolve around me:  I picked the coordinate system!"





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