Scroll to navigation

Geo::Point(3pm) User Contributed Perl Documentation Geo::Point(3pm)


Geo::Point - a point on the globe


   is a Geo::Shape


 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);


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 latlong(), longlat(), xy(), and yx().
Extends "DESCRIPTION" in Geo::Shape.


Extends "METHODS" in Geo::Shape.


Extends "Constructors" in Geo::Shape.
Geo::Point->fromString($string, [$projection])
Create a new point from a $string. The coordinates can be separated by a comma (preferrably), 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:
  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 "d", single or double quote, or trailing/leading "e", "w", "n", "s" (either lower or upper-case) will force a latlong projection. Those coordinates must follow the rules of dms2deg().
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 $@;
$obj->latlong([ $lat,$long,[$proj] ] | [$proj])
Geo::Point->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 Geo::Proj. See also longlat(), xy(), and yx().
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');
$obj->longlat([ $long,$lat,[$proj] ] | [$proj])
Geo::Point->longlat([ $long,$lat,[$proj] ] | [$proj])
Like latlong(), but with the coordinates reversed. Some applications prefer this.
 -Option   --Defined in     --Default
  lat                         undef
  latitude                    undef
  long                        undef
  longitude                   undef
  proj       Geo::Shape       see Geo::Proj::defaultProjection()
  x                           undef
  y                           undef
latitude => COORDINATE
longitude => COORDINATE
proj => LABEL
$obj->xy([$x, $y, [$proj] ] | [$proj])
Geo::Point->xy([$x, $y, [$proj] ] | [$proj])
Like longlat() but now for carthesian projections. Usually, the coordinate order is reversed. See also yx().
$obj->yx([$y, $x, [$proj] ] | [$proj])
Geo::Point->yx([$y, $x, [$proj] ] | [$proj])
Like latlong() but now for carthesian projections. Usually, the coordinate order is reversed. See also xy().


Extends "Attributes" in Geo::Shape.
Inherited, see "Attributes" in Geo::Shape
Inherited, see "Attributes" in Geo::Shape


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


Extends "Projections" in Geo::Shape.
Inherited, see "Projections" in Geo::Shape
Be sure the that coordinates are between -180/180 longitude, -90/90 lattitude. No changes for non-latlong projections.
$obj->projectOn($nick, @points)
Inherited, see "Projections" in Geo::Shape


Extends "Geometry" in Geo::Shape.
Always returns zero.
The bounding box of a point contains twice itself.
Inherited, see "Geometry" in Geo::Shape
$obj->bboxRing([$xmin, $ymin, $xmax, $ymax, [$proj]])
Geo::Point->bboxRing([$xmin, $ymin, $xmax, $ymax, [$proj]])
Inherited, see "Geometry" in Geo::Shape
$obj->distance($object, [$unit])
Inherited, see "Geometry" in Geo::Shape
$obj->distancePointPoint($geodist, $units, $point)
Compute the distance between the current point and some other $point in $units. The $geodist object will do the calculations. See distance().
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.
Always returns zero.
$obj->sameAs($other, $tolerance)


Extends "Display" in Geo::Shape.
Returns the coordinates in their usual order, formatted as string with a joining blank;
Returns the coordinates in the order which is usual for the projection used.
$obj->deg2dm($degrees, $pos, $neg)
Geo::Point->deg2dm($degrees, $pos, $neg)
Inherited, see "Display" in Geo::Shape
$obj->deg2dms($degrees, $pos, $neg)
Geo::Point->deg2dms($degrees, $pos, $neg)
Inherited, see "Display" in Geo::Shape
Like dms(), but doesn't show seconds.
Like dmsHTML(), but does not show seconds.
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 dmsHTML()).
Inherited, see "Display" in Geo::Shape
Like dms(), but all character which are troublesome for HTML are translated into character codes.
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);
 print $point->long;   # -181;
Returns a string representation of the point, which is also used for stringification. The default projection is the one of the point.
 print "Point: ",$gp->toString, "\n";
 print "Point: $gp\n";   # same
 print "Point: ",$gp->toString('clrk66'), "\n";


Extends "OVERLOAD" in Geo::Shape.
overload: '""' (stringification)
Inherited, see "OVERLOAD" in Geo::Shape
overload: 'bool' (truth value)
Inherited, see "OVERLOAD" in Geo::Shape


Error: UTM requires 3 values: easting, northing, and zone
Error: can only compare a point to another Geo::Point
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.
Error: dms latitude coordinate not understood: $string
See dms2deg() for permitted formats.
Error: dms longitude coordinate not understood: $string
See dms2deg() for permitted formats.
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 upto 60) and an optional latitude indication (C upto X, except I and O).
Error: illegal character in x coordinate $x
Error: illegal character in y coordinate $y
Error: in() not implemented for a $class
Error: too few values in $string (got @parts)
Most projection require two parameters, but utm requires three (with zone).
Error: too many values in $string (got @parts)
Most projection require two parameters, but utm requires three (with zone).
Error: undefined projection $proj for $string
The projection you used (or is set as default) is not defined. See Geo::Proj::new() about how to defined them.


This module is part of Geo-Point distribution version 0.96, built on January 21, 2014. Website: All modules in this suite: "Geo::Point", "Geo::Proj4", "Geo::WKT", "Math::Polygon", "Geo::GML", "Geo::ISO19139", "Geo::EOP", "Geo::Format::Envisat", and "Geo::Format::Landsat".
Please post questions or ideas to the mailinglist at


Copyrights 2005-2014 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
2014-01-21 perl v5.18.2