Geo::HelmertTransform - perform "Helmert" transformations between coordinates

       Written by Chris Lightfoot, team@mysociety.org

       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.

perl v5.36.0                                       2022-11-20                         Geo::HelmertTransform(3pm)

       Latitude is expressed in degrees, positive-north; longitude in degrees, positive-east. Heights
       (ellipsoid) and cartesian coordinates are in meters.

       Perform transformations between geographical coordinates in different datums.

       It is usual to describe geographical points in terms of their polar coordinates (latitude, longitude and
       altitude) referenced to a "datum ellipsoid", which is used to approximate the Earth's geoid. The
       latitude, longitude and altitude of a given physical point vary depending on which datum ellipsoid is in
       use.  Unfortunately, a number of ellipsoids are in everyday use, and so it is often necessary to
       transform geographical coordinates between different datum ellipsoids.

       Two different datum ellipsoids may differ in the locations of their centers, or in their shape; and there
       may be an angle between their equatorial planes or the meridians relative to which longitude is measured.
       The Helmert Transform, which this module implements, is a linear transformation of coordinates between
       pairs of datum ellipsoids in the limit of small angles of deviation between them.

       rad_to_deg RADIANS
           Convert RADIANS to degrees.

       deg_to_rad DEGREES
           Convert DEGREES to radians.

       geo_to_xyz DATUM LAT LON H
           Return  the  Cartesian  (X,  Y,  Z) coordinates for the geographical coordinates (LAT, LON, H) in the
           given DATUM.

       xyz_to_geo DATUM X Y Z
           Return the geographical (LAT, LON, H) coordinates for the Cartesian coordinates  (X,  Y,  Z)  in  the
           given DATUM. This is an iterative procedure.

       convert_datum D1 D2 LAT LON H
           Given  geographical  coordinates  (LAT,  LON, H) in datum D1, return the corresponding coordinates in
           datum D2. This assumes that the transformations are small, and always converts via WGS84.

       datum NAME
           Return the datum of the given NAME. Currently implemented are:

           Airy1830
               The 1830 Airy ellipsoid to which the British Ordnance Survey's National Grid is referenced.

           Airy1830Modified
               The modified 1830 Airy ellipsoid to which the Irish Grid (as used by Ordnance Survey Ireland  and
               Ordnance Survey Northern Ireland); also known as the Ireland 1975 datum.

           WGS84
               The global datum used for GPS.

       Geo::HelmertTransform - perform "Helmert" transformations between coordinates

AguidetocoordinatesystemsinGreatBritain, http://www.gps.gov.uk/guidecontents.aspMakingmapscompatiblewithGPS, http://www.osni.gov.uk/downloads/Making%20maps%20GPS%20compatible.pdf

           use Geo::HelmertTransform;

           my ($lat, $lon, $h) = ...; # from OS map
           my $airy1830 = Geo::HelmertTransform::datum('Airy1830');
           my $wgs84 = Geo::HelmertTransform::datum('WGS84');

           ($lat, $lon, $h)
               = Geo::HelmertTransform::convert_datum($airy1830, $wgs84,
                                                       $lat, $lon, $h);

       1.14