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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:

```GREAT CIRCLE DISTANCES
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
ans.

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,
Zaxo

• Comment on Re: Distance Between Geographical Coordinates

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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?

Abigail

go north zero (or less) units ;P

~Particle *accelerates*

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