=encoding utf8

=head1 NAME

Geo::Shape - base class for 2-dimensional points on the earth surface

=head1 INHERITANCE

 Geo::Shape is extended by
   Geo::Line
   Geo::Point
   Geo::Space
   Geo::Surface

=head1 SYNOPSIS

 use Geo::Shape;

 my $p1 = Geo::Point->new(lat => 2.17, ...);
 my $p2 = Geo::Point->latlong(2.17, 3.14);   # wgs84 is default

 my $p3 = $p1->in('wgs84');                  # conversion
 my $p4 = $p1->in('utm');                    # conversion

=head1 DESCRIPTION

Base class for the many geo-spatial objects defined by the GeoPoint
distribution.

=head1 METHODS

=head2 Constructors

=over 4

=item $obj-E<gt>B<new>(%options)

=item Geo::Shape-E<gt>B<new>(%options)

Create a new object.

 -Option--Default
  proj    see Geo::Proj::defaultProjection()

=over 2

=item proj => LABEL

=back

=back

=head2 Attributes

=over 4

=item $obj-E<gt>B<proj>()

Returns the nickname of the projection used by the component.
B<Be warned:> this is not a L<Geo::Point|Geo::Point> object, but just a label.

=item $obj-E<gt>B<proj4>()

Returns the proj4 object which handles the projection.

=back

=head2 Projections

=over 4

=item $obj-E<gt>B<in>( <$label|'utm'> )

The coordinates of this point in a certain projection, refered to with
the $label.  The projection is defined with L<new()|Geo::Shape/"Constructors">.  When simply
'utm' is provided, the best UTM zone is selected.

In LIST context, the coordinates are returned.  In SCALAR context,
a new object is returned.

example: 

  my $gp       = Geo::Point->latlong(1,2);

  # implicit conversion to wgs84, if not already in latlong
  my ($lat, $long) = $pr->latlong;

  # will select an utm zone for you
  my $p_utm    = $gp->in('utm');
  my ($x, $y)  = $p_utm->xy;
  my $label    = $p_utm->proj;
  my ($datum, $zone) = $label =~ m/^utm-(\w+)-(\d+)$/;

=item $obj-E<gt>B<projectOn>($nick, @points)

The @points are ARRAYs with each an X and Y coordinate of a single
point in space.  A list of transformed points is returned, which is empty
if no change is needed.  The returned list is preceded by the projection
nick of the result; usually the same as the provided $nick, but in
some cases (for instance UTM) it may differ.

=back

=head2 Geometry

=over 4

=item $obj-E<gt>B<area>()

Returns the area covered by the geo structure. Points will return zero.

=item $obj-E<gt>B<bbox>()

Returns the bounding box of the object as four coordinates, respectively
xmin, ymin, xmax, ymax.  The values are expressed in the coordinate
system of the object.

=item $obj-E<gt>B<bboxCenter>()

Returns a L<Geo::Point|Geo::Point> which represent the middle of the object.  It is
the center of the bounding box.  The values is cached, once computed.

Be warned that the central point in one projection system may be quite
different from the central point in some other projectionsystem .

=item $obj-E<gt>B<bboxRing>( [$xmin, $ymin, $xmax, $ymax, [$proj]] )

=item Geo::Shape-E<gt>B<bboxRing>( [$xmin, $ymin, $xmax, $ymax, [$proj]] )

Returns a L<Geo::Line|Geo::Line> which describes the outer bounds of the
object called upon, counter-clockwise and left-bottom first.  As class
method, you need to specify the limits and the PROJection.

=item $obj-E<gt>B<distance>( $object, [$unit] )

Calculate the distance between this object and some other object.
For many combinations of objects this is not supported or only
partially supported.

This calculation is performed with L<Geo::Distance> in accurate mode.
The default $unit is kilometers.  Other units are provided in the manual
page of L<Geo::Distance>.  As extra unit, C<degrees> and C<radians> are
added as well as the C<km> alias for kilometer.

=item $obj-E<gt>B<perimeter>()

Returns the length of the outer border of the object's components.  For
points, this returns zero.

=back

=head2 Display

=over 4

=item $obj-E<gt>B<deg2dm>($degrees, $pos, $neg)

=item Geo::Shape-E<gt>B<deg2dm>($degrees, $pos, $neg)

Like L<deg2dms()|Geo::Shape/"Display"> but without showing seconds.

example: 

 print $point->deg2dm(0.12, 'e', 'w');
 print Geo::Shape->deg2dm(0.12, 'e', 'w');

=item $obj-E<gt>B<deg2dms>($degrees, $pos, $neg)

=item Geo::Shape-E<gt>B<deg2dms>($degrees, $pos, $neg)

Translate floating point $degrees into a "degrees minutes seconds"
notation.  An attempt is made to handle rounding errors.

example: 

 print $point->deg2dms(-12.34, 'E', 'W');'     # --> 12d20'24"W
 print Geo::Shape->deg2dms(52.1234, 'E', 'W'); # --> 52d07'24"E

=item $obj-E<gt>B<dms2deg>($dms)

=item Geo::Shape-E<gt>B<dms2deg>($dms)

Accepts for instance 3d12'24.123, 3d12"E, 3.12314w, n2.14, s3d12",
-12d34, and returns floating point degrees.

=back

=head1 OVERLOAD

=over 4

=item overload: B<'""' (stringification)>

Returns a string "$proj($lat,$long)" or "$proj($x,$y)".  The C<$proj>
is the nickname you have assigned to the projection.

=item overload: B<'bool' (truth value)>

A point is always true: defined.

=back

=head1 DIAGNOSTICS

=over 4

=item Error: distance calculation not implemented between a $kind and a $kind

Only a subset of all objects can be used in the distance calculation.
The limitation is purely caused by lack of time to implement this.

=item Error: in() not implemented for a $class

=back

=head1 SEE ALSO

This module is part of Geo-Point distribution version 0.97,
built on January 23, 2018. Website: F<http://perl.overmeer.net/CPAN/>

=head1 LICENSE

Copyrights 2005-2018 by [Mark Overmeer]. For other contributors see ChangeLog.

This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
See F<http://dev.perl.org/licenses/>

