Geo-CheapRuler

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Geo::CheapRuler

A collection of very fast approximations to common geodesic measurements. Useful for performance-sensitive code that measures things on a city scale (less than 500km, not near the poles). Can be an order of magnitude faster than Haversine based metho...

A Perl port of Mapbox's cheap-ruler v4.0.0 https://github.com/mapbox/cheap-ruler

Very fast as they use just 1 trig function per call.

The Maths model is based upon the Earth's actual shape (a squashed sphere). For 'city' scale work, it is more accurate than
the Haversine formulae (which uses several trig calls based upon a spherical Earth). The Cheap\_Ruler Github page explains it better!

See:
	
	https://github.com/aavmurphy/CheapRuler/REAME.md

INSTALLATION

To install this module, run the following commands:

	perl Makefile.PL

lib/Geo/CheapRuler.pm  view on Meta::CPAN

A collection of very fast approximations to common geodesic measurements. Useful for performance-sensitive code that measures things on a city scale (less than 500km, not near the poles).
Can be an order of magnitude faster than Haversine based methods.

A Perl port of Mapbox's cheap-ruler v4.0.0 https://github.com/mapbox/cheap-ruler

Very fast as they use just 1 trig function per call.

=head1 MATHS MODEL

The Maths model is based upon an approximation to Vincenty's formulae, which uses the Earth's actual shape, an oblate ellipsoid (squashed sphere). For 'city' scale work, it is still more accurate than
the Haversine formulae (which uses several trig calls based upon a spherical Earth). For an explanation, see
https://blog.mapbox.com/fast-geodesic-approximations-with-cheap-ruler-106f229ad016

=head1 EXPORT

Nothing

=head1 WEBSITE

https://github.com/aavmurphy/CheapRuler

lib/Geo/CheapRuler.pm  view on Meta::CPAN

	$ruler = CheapRuler->new(35.05, 'miles');

=cut

sub   new ( $class, $lat, $units='kilometers' ) {
       croak( 'No latitude given.') if ! defined $lat; 
       croak( "Unknown unit $units. Use one of: " + join( ', ', keys(%FACTORS) ) ) if $units && ! $FACTORS{ $units };

		my $self = bless {};

        # Curvature formulas from https://en.wikipedia.org/wiki/Earth_radius#Meridional
        my $m		= $RAD * $RE * ( $units ? $FACTORS{ $units } : 1 );
        my $coslat	= cos( $lat * $RAD );
        my $w2		= 1 / (1 - $E2 * (1 - $coslat**2) );
        my $w		= sqrt($w2);

        # multipliers for converting longitude and latitude degrees into distance
        $self->{kx} = $m * $w * $coslat;        # based on normal radius of curvature
        $self->{ky} = $m * $w * $w2 * (1 - $E2); # based on meridonal radius of curvature
		
		return $self;

lib/Geo/CheapRuler.pm  view on Meta::CPAN

    return $deg;
	}


=head1 SEE ALSO

GIS::Distance

	https://metacpan.org/pod/GIS::Distance

	Group of modules with XS versions which implement Haversine and Vincenty distance formulas

	Consider for longer than 'city scale' distances, or near the Poles.

GIS::Distance::Vincenty

	The more accurate formulae which this module approximates. There is an XS version of it.

	https://metacpan.org/pod/GIS::Distance::Vincenty

=head1 SUPPORT

You can find documentation for this module with the perldoc command.

    perldoc Geo::CheapRuler

Or at