GIS::Distance::Formula::GreatCircle - Great circle distance calculations. (BROKEN)

GIS-Distance documentation Contained in the GIS-Distance distribution.

Index

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NAME

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GIS::Distance::Formula::GreatCircle - Great circle distance calculations. (BROKEN)

DESCRIPTION

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A true Great Circle Distance calculation. This was created because the GIS::Distance::MathTrig calculation uses Math::Trig's great_circle_distance() which doesn't actually appear to use the actual Great Circle Distance formula.

Normally this module is not used directly. Instead GIS::Distance is used which in turn interfaces with the various formula classes.

BROKEN

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As documented in more detail at the BUGS section of GIS::Distance, the distances returned by this module seem to be invalid. Don't use this module unless you want to help fix it.

FORMULA

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  c = 2 * asin( sqrt(
    ( sin(( lat1 - lat2 )/2) )^2 + 
    cos( lat1 ) * cos( lat2 ) * 
    ( sin(( lon1 - lon2 )/2) )^2
  ) )

METHODS

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distance

This method is called by GIS::Distance's distance() method.

SEE ALSO

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GIS::Distanc

AUTHOR

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Aran Clary Deltac <bluefeet@cpan.org>

LICENSE

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This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

GIS-Distance documentation Contained in the GIS-Distance distribution. 
package GIS::Distance::Formula::GreatCircle;


use Any::Moose;
use namespace::autoclean;

with 'GIS::Distance::Formula';

use Class::Measure::Length qw( length );
use Math::Trig qw( deg2rad asin );


sub distance {
    my($self,$lat1,$lon1,$lat2,$lon2) = @_;
    $lon1 = deg2rad($lon1); $lat1 = deg2rad($lat1);
    $lon2 = deg2rad($lon2); $lat2 = deg2rad($lat2);

    my $c = 2*asin( sqrt(
        ( sin(($lat1-$lat2)/2) )^2 + 
        cos($lat1) * cos($lat2) * 
        ( sin(($lon1-$lon2)/2) )^2
    ) );

    return length( $self->kilometer_rho() * $c, 'km' );
}

__PACKAGE__->meta->make_immutable;

1;
__END__