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# Geo::Coordinates::CH1903Plus
# Conversion between WGS84 and Swiss CH1903+ (aka LV95).
#
# Copyright (c) 2012 UK Citizens Online Democracy. This module is free
# software; you can redistribute it and/or modify it under the same terms as
# Perl itself.
#
# WWW: http://www.mysociety.org/
package Geo::Coordinates::CH1903Plus;
$Geo::Coordinates::CH1903Plus::VERSION = '1.00';
use strict;
# Use the same calcs as CH1903 but with offset.
# Maximum distortion is 3M which should be sufficient for our purposes.
use constant LV95_X_OFFSET => 2000000;
use constant LV95_Y_OFFSET => 1000000;
=head1 NAME
Geo::Coordinates::CH1903Plus
=head1 VERSION
1.00
=head1 SYNOPSIS
use Geo::Coordinates::CH1903Plus;
my ($lat, $lon) = ...;
my ($e, $n) = Geo::Coordinates::CH1903Plus::from_latlon($lat, $lon);
my ($lat, $lon) = Geo::Coordinates::CH1903Plus::to_latlon($e, $n);
=head1 FUNCTIONS
=over 4
=cut
sub from_latlon($$) {
my ($lat, $lon) = @_;
$lat *= 3600;
$lon *= 3600;
my $lat_aux = ($lat - 169028.66) / 10000;
my $lon_aux = ($lon - 26782.5) / 10000;
my $x = 600072.37 + LV95_X_OFFSET
+ (211455.93 * $lon_aux)
- (10938.51 * $lon_aux * $lat_aux)
- (0.36 * $lon_aux * $lat_aux**2)
- (44.54 * $lon_aux**3);
my $y = 200147.07 + LV95_Y_OFFSET
+ (308807.95 * $lat_aux)
+ (3745.25 * $lon_aux**2)
+ (76.63 * $lat_aux**2)
- (194.56 * $lon_aux**2 * $lat_aux)
+ (119.79 * $lat_aux**3);
return ($x, $y);
}
sub to_latlon($$) {
my ($x, $y) = @_;
my $x_aux = ($x - 600000 - LV95_X_OFFSET) / 1000000;
my $y_aux = ($y - 200000 - LV95_Y_OFFSET) / 1000000;
my $lat = 16.9023892
+ (3.238272 * $y_aux)
- (0.270978 * $x_aux**2)
- (0.002528 * $y_aux**2)
- (0.0447 * $x_aux**2 * $y_aux)
- (0.0140 * $y_aux**3);
my $lon = 2.6779094
+ (4.728982 * $x_aux)
+ (0.791484 * $x_aux * $y_aux)
+ (0.1306 * $x_aux * $y_aux**2)
- (0.0436 * $x_aux**3);
$lat = $lat * 100 / 36;
$lon = $lon * 100 / 36;
return ($lat, $lon);
}
=head1 AUTHOR AND COPYRIGHT
Maths courtesy of the Swiss Federal Office of Topography:
http://www.swisstopo.admin.ch/internet/swisstopo/en/home/products/software/products/skripts.html
Written by Matthew Somerville
Copyright (c) UK Citizens Online Democracy.
This module is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
=cut
1;
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