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#
# Coordinates system related functions
#
package OpenGL::Earth::Coords;
# (1/360.0) * 2 * 3.14159265
use constant DEG_TO_RAD => 0.0174532925;
# Convert earth latitude/longitude to 3D coords
sub earth_to_xyz ($$$) {
    my ($lat, $lon, $radius) = @_;
    $lat *= DEG_TO_RAD;
    $lon *= DEG_TO_RAD;
        my $cos_lat = $radius * cos($lat);
    my $x = $cos_lat * cos($lon);
    my $y = $cos_lat * sin($lon);
    my $z = $radius  * sin($lat);
    return ($x, $y, $z);
}
1;
__END__
HideShow 28 lines of Pod
=pod
=head1 NAME
OpenGL::Earth::Coords
=head1 SYNOPSIS
    # Where's Oslo on a 3D Sphere of radius 1.0?
    use OpenGL::Earth::Coords;
    my ($x, $y, $z) = OpenGL::Earth::Coords::earth_to_xyz(59.9167, 10.75, 1.0);
    printf "x=%.3f y=%.3f z=%.3f\n", $x, $y, $z;
=head1 DESCRIPTION
Just a quick and dirty module to convert lat/long coordinates
into 3D x, y, z coordinates, assuming the Earth is a perfect
sphere, which we know is not.
=head1 AUTHORS
Cosimo Streppone, cosimo@cpan.org
=head1 COPYRIGHT
This program is free software, you can redistribute it and/or modify it under
the same terms as Perl itself.