Provided by: libgeo-point-perl_0.94-1_all 
NAME
Geo::Proj - Handling projections
SYNOPSIS
use Geo::Proj;
my $wgs84 = Geo::Proj->new # predefined if import()
( nick => 'wgs84'
, proj4 => '+proj=latlong +datum=WGS84 +ellps=WGS84'
);
my $clrk = Geo::Proj->new
( nick => 'clark66'
, proj4 => [proj => "merc", ellps => "clrk66", lon_0 => -96]
);
my $point_wgs84= Geo::Point->latlong(56.12, 4.40, 'wgs84');
my $point_wgs84= Geo::Point->latlong(56.12, 4.40, $wgs84);
my $point_clrk = $point_wgs84->in($clrk);
my $point_clrk = Geo::Proj->to($wgs84, $clrk, $point_wgs84);
my $point_clrk = Geo::Proj->to($wgs84, 'clark66', $point_wgs84);
DESCRIPTION
A point on Earth's surface can be represented in many different coordinate systems. The
Geo::Proj4 module wraps the popular Open Source "libproj" library to convert between those
coordinate systems; a very complex job.
Within a program, however, you like some extra abstraction from that library: to be able
to simply label a point to its system, and then forget about all transformations which may
be necessary. The label (or "nick") hides all complicated parameters for the actual
projection .
WARNING 1: this class will collect all nicks, which means that calling new() with the same
label twice will have the second ignored.
WARNING 2: the wgs84 nickname is predefined, but only if this module is 'used' with
import. So if you decide to use 'require' to dynamically load this module, then don't
forget to call 'import()' yourself, or define the wgs84 projection yourself.
METHODS
Constructors
Geo::Proj->new([NICK], OPTIONS)
Create a new object.
-Option--Default
name <from proj4>
nick <required>
proj4 <required>
srid undef
name => STRING
nick => LABEL
The abbrevated name for this projection.
proj4 => OBJECT|ARRAY|STRING
The ARRAY or STRING will by used to create a Geo::Proj4 object by calling
Geo::Proj4::new(). You may also specify such an prepared OBJECT.
srid => INTEGER
SRID stands for "Spatial Reference System ID", which is just an index in a table of
spatial descriptions as used by SQL. Only INTEGER values larger than 0 are
permitted.
Attributes
$obj->name()
The full, official name of the projection
$obj->nick()
Simple abbreviating of the projection.
$obj->proj4([NICK|PROJ4])
Geo::Proj->proj4([NICK|PROJ4])
Returns the projection library handle (a Geo::Proj4) to be used by this component. As
class method, the NICK is specified for a lookup. In case a PROJ4 is specified, that
is returned.
example:
my $wgs84 = Geo::Proj->new(nick => 'wgs84', ...);
my $wgs84_proj4 = Geo::Proj->proj4('wgs84');
my $wgs84_proj4 = Geo::Proj->proj4($wgs84);
my $wgs84_proj4 = $wgs84->proj4;
$obj->srid()
The "Spatial Reference System ID" if known.
Projecting
Geo::Proj->defaultProjection([NICK|PROJ])
The NICK must be defined with new(). Returned is the Geo::Proj object for the default
projection. The default is the first name created, which probably is 'wgs84' (when
import() had a chance)
Geo::Proj->dumpProjections([FILEHANDLE])
Print details about the defined projections to the FILEHANDLE, which defaults to the
selected. Especially useful for debugging.
Geo::Proj->listProjections()
Returns a sorted lost of projection nicks.
Geo::Proj->projection(NICK|PROJ)
Returns the Geo::Proj object, defined with NICK. In case such an object is passed in
as PROJ, it is returned unaffected. This method is used where in other methods NICKS
or PROJ can be used as arguments.
example:
my $wgs84 = Geo::Proj->projection('wgs84');
my $again = Geo::Proj->projection($wgs84);
$obj->to([PROJ|NICK], PROJ|NICK, POINT|ARRAY-OF-POINTS)
Geo::Proj->to([PROJ|NICK], PROJ|NICK, POINT|ARRAY-OF-POINTS)
Expects an Geo::Proj to project the POINT or POINTS to. The work is done by
Geo::Proj4::transform(). As class method, you have to specify two nicks or
projections.
Be warned that this to() method expects POINTs which are not Geo::Point objects, but
which themselves are an ARRAY containing X,Y and optionally a Z coordinate.
example:
my $p2 = $wgs84->to('utm31-wgs84', $p1);
my $p2 = $wgs84->to($utm, $p1);
my $p2 = Geo::Proj->to('wgs84', 'utm31-wgs84', $p1);
UTM
Geo::Proj->UTMprojection(DATUM|PROJ|undef, ZONE)
The PROJ is a Geo::Proj which is used to collect the datum information from if no
DATUM was specified explicitly. It may also be a string which is the name of a datum,
as known by proj4. Undef will be replaced by the default projection.
example:
my $proj = Geo::Proj->UTMprojection('WGS84', 31) or die;
print $proj->nick; # for instance utm31-wgs84
$obj->bestUTMprojection(POINT, [PROJ|NICK])
Geo::Proj->bestUTMprojection(POINT, [PROJ|NICK])
Returns the best UTM projection for some POINT. As class method, you specify the
nickname or the object for the point.
example:
my $point = Geo::Point->longlat(2.234, 52.12);
my $proj = Geo::Proj->bestUTMprojection($point);
print $proj->nick; # for instance utm31-wgs84
$obj->zoneForUTM(POINT)
Geo::Proj->zoneForUTM(POINT)
Provided some point, figure-out which zone is most optimal for representing the point.
In LIST context, zone number, zone letter, and meridian are returned as separate
scalars. In LIST context, the zone number and letter are returned as one..
This code is stolen from Geo::Coordinates::UTM, because that module immediately starts
to do computations with this knowledge, which is not wanted here. Probably a lot of
zones are missing.
OVERLOADING
overload: '""' (stringification)()
Returns the nick-name for this projection.
SEE ALSO
This module is part of Geo-Point distribution version 0.94, built on December 21, 2012.
Website: http://perl.overmeer.net/geo/ 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 http://geo-perl@list.hut.fi
LICENSE
Copyrights 2005-2012 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 http://www.perl.com/perl/misc/Artistic.html