=encoding utf8

=head1 NAME

Geo::Point - a point on the globe

=head1 INHERITANCE

 Geo::Point
   is a Geo::Shape

=head1 SYNOPSIS

 use Geo::Point;

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

 my $w = Geo::Proj->new(wgs84 => ...);
 my $p = Geo::Point->latlong(1,2, 'wgs84');

 my ($lat, $long) = $p->latlong;
 my ($x, $y) = $p->xy;
 my ($x, $y) = $p->in('utm31-wgs84');

 my $p = Geo::Point->xy(1,2);

=head1 DESCRIPTION

One location on the globe, in any coordinate system.  This package tries
to hide the maths and the coordinate system in which the point is
represented.

One of the most confusing things when handling geometrical data, is
that sometimes latlong, sometimes xy are used: horizontal and vertical
organization reversed.  This package tries to hide this from your
program by providing abstract accessors L<latlong()|Geo::Point/"Constructors">, L<longlat()|Geo::Point/"Constructors">,
L<xy()|Geo::Point/"Constructors">, and L<yx()|Geo::Point/"Constructors">.

Extends L<"DESCRIPTION" in Geo::Shape|Geo::Shape/"DESCRIPTION">.
 
=head1 METHODS

Extends L<"METHODS" in Geo::Shape|Geo::Shape/"METHODS">.
 
=head2 Constructors

Extends L<"Constructors" in Geo::Shape|Geo::Shape/"Constructors">.
 
=over 4

=item Geo::Point-E<gt>B<fromString>( $string, [$projection] )

Create a new point from a $string.  The coordinates can be separated by
a comma (preferably), or blanks.  When the coordinates end on NSEW, the
order does not matter, otherwise lat-long or xy order is presumed.

This routine is very smart.  It understands:

  PROJLABEL VALUE VALUE
  PROJLABEL: VALUE VALUE
  PROJLABEL, VALUE, VALUE
  PROJLABEL: VALUE, VALUE
  VALUE VALUE
  VALUE, VALUE
  utm: ZONE, VALUE, VALUE   # also without commas and ':'
  utm: VALUE, VALUE, ZONE   # also without commas and ':'
  utm: VALUE, VALUE         # also without commas and ':'
  ZONE, VALUE, VALUE        # also without commas and ':'
  VALUE, VALUE, ZONE        # also without commas and ':'

The VALUE must be suitable for projection.  If only two values are
provided, a C<d>, single or double quote, or trailing/leading C<e>, C<w>,
C<n>, C<s> (either lower or upper-case) will force a latlong projection.
Those coordinates must follow the rules of L<dms2deg()|Geo::Shape/"Display">.

example: point from string

 my $x = 'utm 31n 12311.123 34242.12'; # utm zone 31N
 my $x = '12311.123 34242.12 31';      # utm zone 31
 my $x = '123.123E 12.34';             # wgs84  latlong
 my $x = 'clrk66 123.123 12.34';       # clrk66 latlong
 my $x = '12d34'123.1W 11.1123';       # wgs84  longlat

 my $p = Geo::Point->fromString($x);

 # When parsing user applications, you probably want:
 my $p = eval { Geo::Point->fromString($x) };
 warn $@ if $@;

=item $obj-E<gt>B<latlong>( [ $lat,$long,[$proj] ] | [$proj] )

=item Geo::Point-E<gt>B<latlong>( [ $lat,$long,[$proj] ] | [$proj] )

When called as class method, you create a new point.  Provide a LATitude
and LONGitude. The optional PROJection tells in which coordinate system.

As instance method, the latitude and longitude are reported.  You
can ask it to be translated into the $proj coordinate system first.

When $proj is undefined, none is presumed. The project must be specified
as string, which referse to a projection defined by L<Geo::Proj|Geo::Proj>.
See also L<longlat()|Geo::Point/"Constructors">, L<xy()|Geo::Point/"Constructors">, and L<yx()|Geo::Point/"Constructors">.

example: latlong as class method

 my $wgs84 = Geo::Proj->new(wgs84 => ...);
 my $gp    = Geo::Point->latlong(52.3213, 5.53, 'wgs84');

example: latlong as instance method

 my ($lat, $long) = $gp->latlong('wgs84');

=item $obj-E<gt>B<longlat>( [ $long,$lat,[$proj] ] | [$proj] )

=item Geo::Point-E<gt>B<longlat>( [ $long,$lat,[$proj] ] | [$proj] )

Like L<latlong()|Geo::Point/"Constructors">, but with the coordinates reversed.  Some applications
prefer this.

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

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

 -Option   --Defined in     --Default
  lat                         undef
  latitude                    undef
  long                        undef
  longitude                   undef
  proj       Geo::Shape       see Geo::Proj::defaultProjection()
  x                           undef
  y                           undef

=over 2

=item lat => COORDINATE

=item latitude => COORDINATE

=item long => COORDINATE

=item longitude => COORDINATE

=item proj => LABEL

=item x => COORDINATE

=item y => COORDINATE

=back

=item $obj-E<gt>B<xy>( [$x, $y, [$proj] ] | [$proj] )

=item Geo::Point-E<gt>B<xy>( [$x, $y, [$proj] ] | [$proj] )

Like L<longlat()|Geo::Point/"Constructors"> but now for carthesian projections.  Usually, the coordinate
order is reversed.  See also L<yx()|Geo::Point/"Constructors">.

=item $obj-E<gt>B<yx>( [$y, $x, [$proj] ] | [$proj] )

=item Geo::Point-E<gt>B<yx>( [$y, $x, [$proj] ] | [$proj] )

Like L<latlong()|Geo::Point/"Constructors"> but now for carthesian projections.  Usually, the
coordinate order is reversed.  See also L<xy()|Geo::Point/"Constructors">.

=back

=head2 Attributes

Extends L<"Attributes" in Geo::Shape|Geo::Shape/"Attributes">.
 
=over 4

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

Inherited, see L<Geo::Shape/"Attributes">

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

Inherited, see L<Geo::Shape/"Attributes">

=back

=head2 Accessors

The accessors only work correctly when you are sure that the point is
in the right coordinate systems.

=over 4

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

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

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

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

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

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

=back

=head2 Projections

Extends L<"Projections" in Geo::Shape|Geo::Shape/"Projections">.
 
=over 4

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

Inherited, see L<Geo::Shape/"Projections">

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

Be sure the that coordinates are between -180/180 longitude, -90/90
lattitude.  No changes for non-latlong projections.

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

Inherited, see L<Geo::Shape/"Projections">

=back

=head2 Geometry

Extends L<"Geometry" in Geo::Shape|Geo::Shape/"Geometry">.
 
=over 4

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

Always returns zero.

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

The bounding box of a point contains twice itself.

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

Inherited, see L<Geo::Shape/"Geometry">

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

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

Inherited, see L<Geo::Shape/"Geometry">

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

Inherited, see L<Geo::Shape/"Geometry">

=item $obj-E<gt>B<distancePointPoint>($geodist, $units, $point)

Compute the distance between the current point and some other $point in
$units.  The $geodist object will do the calculations.  See L<distance()|Geo::Shape/"Geometry">.

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

Returns a true value if this point is inside the bounding box of
the specified $object.  The borders of the bbox are included.  This is
relatively fast to check, even for complex objects.  When the projections
differ, the point is translated into the $object's coordinate system,
because that one must stay square.

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

Always returns zero.

=item $obj-E<gt>B<sameAs>($other, $tolerance)

=back

=head2 Display

Extends L<"Display" in Geo::Shape|Geo::Shape/"Display">.
 
=over 4

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

Returns the coordinates in their usual order, formatted as string
with a joining blank;

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

Returns the coordinates in the order which is usual for the projection
used.

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

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

Inherited, see L<Geo::Shape/"Display">

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

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

Inherited, see L<Geo::Shape/"Display">

=item $obj-E<gt>B<dm>( [$projection] )

Like L<dms()|Geo::Point/"Display">, but doesn't show seconds.

=item $obj-E<gt>B<dmHTML>( [$projection] )

Like L<dmsHTML()|Geo::Point/"Display">, but does not show seconds.

=item $obj-E<gt>B<dms>( [$projection] )

Show the point as DMS value-pair.  You must be sure that the coordinate
is a projection for which is it useful to represent the values in DMS.
In SCALAR context, one string is returned.  In LIST context, the values
are returned separately in latlong order.

Be warned, that the returned string may contain single and double quote
characters, which may confuse HTML (see L<dmsHTML()|Geo::Point/"Display">).

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

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

Inherited, see L<Geo::Shape/"Display">

=item $obj-E<gt>B<dmsHTML>( [$projection] )

Like L<dms()|Geo::Point/"Display">, but all character which are troublesome for HTML are
translated into character codes.

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

Move a point from the eastern calculations into the western calculations,
resulting in a value below -180.  This is useful when this point is part
of a larger construct, like the corners of a satellite image, which are
both sides of the -180 meridian.

example: moving West

 my $point = Geo::Point->latlong(24, 179);
 $point->moveWest;
 print $point->long;   # -181;

=item $obj-E<gt>B<toString>( [$projection] )

Returns a string representation of the point, which is also used for
stringification.  The default projection is the one of the point.

example: 

 print "Point: ",$gp->toString, "\n";
 print "Point: $gp\n";   # same

 print "Point: ",$gp->toString('clrk66'), "\n";

=back

=head1 OVERLOAD

Extends L<"OVERLOAD" in Geo::Shape|Geo::Shape/"OVERLOAD">.
 
=over 4

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

Inherited, see L<Geo::Shape/"OVERLOAD">

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

Inherited, see L<Geo::Shape/"OVERLOAD">

=back

=head1 DIAGNOSTICS

=over 4

=item Error: UTM requires 3 values: easting, northing, and zone

=item Error: can only compare a point to another Geo::Point

=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: dms latitude coordinate not understood: $string

See L<dms2deg()|Geo::Shape/"Display"> for permitted formats.

=item Error: dms longitude coordinate not understood: $string

See L<dms2deg()|Geo::Shape/"Display"> for permitted formats.

=item Error: illegal UTM zone in $string

A UTM zone can be detected at the beginning or at the end of the
input.  It contains a number (from 1 up to 60) and an optional
latitude indication (C up to X, except I and O).

=item Error: illegal character in x coordinate $x

=item Error: illegal character in y coordinate $y

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

=item Error: too few values in $string (got @parts)

Most projection require two parameters, but utm requires three (with zone).

=item Error: too many values in $string (got @parts)

Most projection require two parameters, but utm requires three (with zone).

=item Error: undefined projection $proj for $string

The projection you used (or is set as default) is not defined.  See
L<Geo::Proj::new()|Geo::Proj/"Constructors"> about how to defined them.

=back

=head1 SEE ALSO

This module is part of Geo-Point distribution version 0.98,
built on February 01, 2019. Website: F<http://perl.overmeer.net/CPAN/>

=head1 LICENSE

Copyrights 2005-2019 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/>