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Distance Calculation Using Latitude And Longitude In Perl

03.17.2010
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        ZIPCodeWorld.com provides this routine to calculate the distance between two points (given the latitude/longitude of those points) in Perl. It is being used to calculate distance between two points lat1, long1 and lat2, long2 and uses radius of earth in kilometers or miles as an argurments using our ZIPCodeWorld(TM) and PostalCodeWorld(TM) products which offer the United States ZIP codes, Canadian Postal Codes, Mexican Postal Codes and North American Area Codes database subscription and solution services.

$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);
}

#::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
#:::  This function get the arccos function using arctan function   :::
#::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
sub acos {
	my ($rad) = @_;
	my $ret = atan2(sqrt(1 - $rad**2), $rad);
	return $ret;
}

#::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
#:::  This function converts decimal degrees to radians             :::
#::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
sub deg2rad {
	my ($deg) = @_;
	return ($deg * $pi / 180);
}

#::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
#:::  This function converts radians to decimal degrees             :::
#::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
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";