search.cpan.org is shutting down
Michael R. Davis > Geo-Horizon-0.02 > Geo::Horizon
Module Version: 0.02

# 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 WGS84`

# METHODS

## 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 radius```

## distance

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 => 1.7```
`  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 => 1.7```
`  Dc = R acos(R / (R + h))`

# BUGS

Please send to the geo-perl email list.

# AUTHOR

Michael R. Davis qw/perl michaelrdavis com/