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Re: Distance Between Geographical Coordinates

by Zaxo (Archbishop)
on Jun 09, 2002 at 23:10 UTC ( #172996=note: print w/replies, xml ) Need Help??

in reply to Distance Between Geographical Coordinates

I believe I mentioned Math::Trig to you. It is in the standard perl distribution. From the pod:

       You can compute spherical distances, called great circle distances, by
       importing the "great_circle_distance" function:

               use Math::Trig 'great_circle_distance'

         $distance = great_circle_distance($theta0, $phi0, $theta1, $phi1, [, $rho]);

       The great circle distance is the shortest distance between two points on a
       sphere.  The distance is in "$rho" units.  The "$rho" is optional, it
       defaults to 1 (the unit sphere), therefore the distance defaults to radi­

       If you think geographically the theta are longitudes: zero at the Green­
       which meridian, eastward positive, westward negative--and the phi are lat­
       itudes: zero at the North Pole, northward positive, southward negative.
       NOTE: this formula thinks in mathematics, not geographically: the phi zero
       is at the North Pole, not at the Equator on the west coast of Africa (Bay
       of Guinea).  You need to subtract your geographical coordinates from pi/2
       (also known as 90 degrees).

         $distance = great_circle_distance($lon0, pi/2 - $lat0,
                                           $lon1, pi/2 - $lat1, $rho);

The pod goes on with an example.

After Compline,

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Re: Distance Between Geographical Coordinates
by Abigail-II (Bishop) on Jun 10, 2002 at 12:17 UTC
    zero at the North Pole, northward positive

    How exactly do I go northward from the North Pole?


      go north zero (or less) units ;P

      ~Particle *accelerates*

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