NAME
Geo::Horizon - Calculate distance to the visual horizon
SYNOPSIS
use Geo::Horizon;
my $gh = Geo::Horizon->new("WGS84");
my $lat=39;
my $alt=1.7;
my $distance_to_horizon=$gh->distance($alt,$lat);
print "Input Lat: $lat1\n";
print "Output Distance: $dist\n";DESCRIPTION
A perl object for calculating the distance to the visual horizon on an ellipsoid.
CONSTRUCTOR
new
my $gh = Geo::Horizon->new(); #default WGS84METHODS
ellipsoid
Method to set or retrieve the current ellipsoid object. The ellipsoid is a Geo::Ellipsoids object.
my $ellipsoid=$gh->ellipsoid; #Default is WGS84
$gh->ellipsoid('Clarke 1866'); #Built in ellipsoids from Geo::Ellipsoids
$gh->ellipsoid({a=>1}); #Custom Sphere 1 unit radiusdistance
The straight-line of sight distance to the horizon: This formula does not take in account radio or optical refraction which will be further the longer the wavelength.
my $dist=$obj->distance($alt, $lat); #alt in meters (ellipsoid units)
#lat in signed decimal degrees
my $dist=$obj->distance($alt); #default lat => 0 (equator)
my $dist=$obj->distance; #default alt => 1.7Formula from http://newton.ex.ac.uk/research/qsystems/people/sque/physics/horizon/
Ds = sqrt(h(2R + h))distance_great_circle
The curved distance along the ellipsoid to the horizon: This is the great circle distance from the track point snapped to the ellipsoid to the visual horizon of the observer.
my $dist=$obj->distance_great_circle($alt, $lat);
my $dist=$obj->distance_great_circle($alt); #default lat => 0
my $dist=$obj->distance_great_circle(); #default alt => 1.7Formula from http://newton.ex.ac.uk/research/qsystems/people/sque/physics/horizon/
Dc = R acos(R / (R + h))TODO
BUGS
Please send to the geo-perl email list.
LIMITS
AUTHOR
Michael R. Davis qw/perl michaelrdavis com/
LICENSE
Copyright (c) 2006 Michael R. Davis (mrdvt92)
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
SEE ALSO
Geo::Ellipsoids Math::Trig