view release on metacpan or  search on metacpan

lib/Geo/Coordinates/OSGB/Background.pod  view on Meta::CPAN

There is no intrinsic merit to using one model or another, but there's
an obvious need to be consistent about which one you choose, and with
the growing ubiquity of GPS systems, it makes sense to standardize on
WGS84.  

The grid remains the primary reference system for use with maps, but
the OS has always also printed a latitude and longitude `graticule' around the 
edges of the large scale sheets.  Traditionally these coordinates have been 
given in the OSGB36 model, but since 2015 the OS has been printing revised 
editions of Explorer and Landranger sheets with WGS84 coordinates instead.
The legend of my recently purchased copy of Explorer 311 has this paragraph under the 
heading `The National Grid Reference System':

=over 4

=item * Base map constructed on Transverse Mercator Projection, Airy Ellipsoid, OSGB (1936) Datum.
Vertical datum mean sea level. The latitude, longitude graticule overlay is on the ETRS89 datum 
and is compatible with the WGS84 datum used by satellite navigation devices.

=back

lib/Geo/Coordinates/OSGB/Grid.pm  view on Meta::CPAN

    $gridref = format_grid(438710.908, 114792.248); # SU 387 147

If you want the individual components call it in a list context.

    ($sq, $e, $n) = format_grid(438710.908, 114792.248); # ('SU', 387, 147)

Note that rather than being rounded, the easting and northing are
B<truncated> to hectometres (as the OS system demands), so the grid
reference refers to the lower left corner of the relevant 100m square.
The system is described below the legend on all OS Landranger maps.

The format grid routine takes an optional third argument to control the
form of grid reference returned.  This should be a hash reference with
one or more of the keys shown below (with the default values).

    format_grid(e, n, {form => 'SS EEE NNN', maps => 0, series => 'ABCHJ'})

=head3 Options for C<format_grid>

=over 4