Calculate Distance and Radius using Latitude and Longitude in Perl

				
=**************************************
= Name: Calculate Distance and Radius using Latitude and Longitude in Perl
= Description:This function calculates the distance between two locations by using latitude and longitude from ZIP code, postal code or postcode. The result is available in miles, kilometers or nautical miles based on great circle distance calculation.
= By: ZipCodeWorld
=
=This code is copyrighted and has= limited warranties.Please see http://www.Planet-Source-Code.com/vb/scripts/ShowCode.asp?txtCodeId=670&lngWId=6=for details.=**************************************

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#::: :::
#::: This routine calculates the distance between two points (given the :::
#::: latitude/longitude of those points). It is being used to calculate :::
#::: the distance between two ZIP Codes or Postal Codes using our:::
#::: ZIPCodeWorld(TM) and PostalCodeWorld(TM) products. :::
#::: :::
#::: Definitions::::
#:::South latitudes are negative, east longitudes are positive:::
#::: :::
#::: Passed to function::::
#:::lat1, lon1 = Latitude and Longitude of point 1 (in decimal degrees) :::
#:::lat2, lon2 = Latitude and Longitude of point 2 (in decimal degrees) :::
#:::unit = the unit you desire for results:::
#:::where: 'M' is statute miles:::
#::: 'K' is kilometers (default):::
#::: 'N' is nautical miles :::
#::: :::
#::: United States ZIP Code/ Canadian Postal Code databases with latitude:::
#::: & longitude are available at http://www.zipcodeworld.com:::
#::: :::
#::: For enquiries, please contact sales@zipcodeworld.com:::
#::: :::
#::: Official Web site: http://www.zipcodeworld.com :::
#::: :::
#::: Hexa Software Development Center © All Rights Reserved 2005:::
#::: :::
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$pi = atan2(1,1) * 4;
sub distance {
	my ($lat1, $lon1, $lat2, $lon2, $unit) = @_;
	my $theta = $lon1 - $lon2;
	my $dist = sin(deg2rad($lat1)) * sin(deg2rad($lat2)) + cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * cos(deg2rad($theta));
 $dist = acos($dist);
 $dist = rad2deg($dist);
 $dist = $dist * 60 * 1.1515;
 if ($unit eq "K") {
 	$dist = $dist * 1.609344;
 } elsif ($unit eq "N") {
 	$dist = $dist * 0.8684;
		}
	return ($dist);
}
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#::: This function get the arccos function using arctan function:::
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sub acos {
	my ($rad) = @_;
	my $ret = atan2(sqrt(1 - $rad**2), $rad);
	return $ret;
}
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#::: This function converts decimal degrees to radians :::
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sub deg2rad {
	my ($deg) = @_;
	return ($deg * $pi / 180);
}
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#::: This function converts radians to decimal degrees :::
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sub rad2deg {
	my ($rad) = @_;
	return ($rad * 180 / $pi);
}
print distance(32.9697, -96.80322, 29.46786, -98.53506, "M") . " Miles\n";
print distance(32.9697, -96.80322, 29.46786, -98.53506, "K") . " Kilometers\n";
print distance(32.9697, -96.80322, 29.46786, -98.53506, "N") . " Nautical Miles\n";