UTM(3pm)						User Contributed Perl Documentation						  UTM(3pm)

NAME

       Geo::Coordinates::UTM - Perl extension for Latitiude Longitude conversions.

SYNOPSIS

       use Geo::Coordinates::UTM;

       my ($zone,$easting,$northing)=latlon_to_utm($ellipsoid,$latitude,$longitude);

       my ($latitude,$longitude)=utm_to_latlon($ellipsoid,$zone,$easting,$northing);

       my ($zone,$easting,$northing)=mgrs_to_utm($mgrs);

       my ($latitude,$longitude)=mgrs_to_latlon($ellipsoid,$mgrs);

       my ($mgrs)=utm_to_mgrs($zone,$easting,$northing);

       my ($mgrs)=latlon_to_mgrs($ellipsoid,$latitude,$longitude);

       my @ellipsoids=ellipsoid_names;

       my($name, $r, $sqecc) = ellipsoid_info 'WGS-84';

DESCRIPTION

       This module will translate latitude longitude coordinates to Universal Transverse Mercator(UTM) coordinates and vice versa.

   Mercator Projection
       The Mercator projection was first invented to help mariners. They needed to be able to take a course and know the distance traveled, and
       draw a line on the map which showed the day's journey. In order to do this, Mercator invented a projection which preserved length, by
       projecting the earth's surface onto a cylinder, sharing the same axis as the earth itself.  This caused all Latitude and Longitude lines to
       intersect at a 90 degree angle, thereby negating the problem that longitude lines get closer together at the poles.

   Transverse Mercator Projection
       A Transverse Mercator projection takes the cylinder and turns it on its side. Now the cylinder's axis passes through the equator, and it
       can be rotated to line up with the area of interest. Many countries use Transverse Mercator for their grid systems.

   Universal Transverse Mercator
       The Universal Transverse Mercator(UTM) system sets up a universal world wide system for mapping. The Transverse Mercator projection is
       used, with the cylinder in 60 positions. This creates 60 zones around the world.  Positions are measured using Eastings and Northings,
       measured in meters, instead of Latitude and Longitude. Eastings start at 500,000 on the centre line of each zone.  In the Northern
       Hemisphere, Northings are zero at the equator and increase northward. In the Southern Hemisphere, Northings start at 10 million at the
       equator, and decrease southward. You must know which hemisphere and zone you are in to interpret your location globally.  Distortion of
       scale, distance, direction and area increase away from the central meridian.

       UTM projection is used to define horizontal positions world-wide by dividing the surface of the Earth into 6 degree zones, each mapped by
       the Transverse Mercator projection with a central meridian in the center of the zone.  UTM zone numbers designate 6 degree longitudinal
       strips extending from 80 degrees South latitude to 84 degrees North latitude. UTM zone characters designate 8 degree zones extending north
       and south from the equator. Eastings are measured from the central meridian (with a 500 km false easting to insure positive coordinates).
       Northings are measured from the equator (with a 10,000 km false northing for positions south of the equator).

       UTM is applied separately to the Northern and Southern Hemisphere, thus within a single UTM zone, a single X / Y pair of values will occur
       in both the Northern and Southern Hemisphere.  To eliminate this confusion, and to speed location of points, a UTM zone is sometimes
       subdivided into 20 zones of Latitude. These grids can be further subdivided into 100,000 meter grid squares with double-letter
       designations. This subdivision by Latitude and further division into grid squares is generally referred to as the Military Grid Reference
       System (MGRS).  The unit of measurement of UTM is always meters and the zones are numbered from 1 to 60 eastward, beginning at the 180th
       meridian.  The scale distortion in a north-south direction parallel to the central meridian (CM) is constant However, the scale distortion
       increases either direction away from the CM. To equalize the distortion of the map across the UTM zone, a scale factor of 0.9996 is applied
       to all distance measurements within the zone. The distortion at the zone boundary, 3 degrees away from the CM is approximately 1%.

   Datums and Ellipsoids
       Unlike local surveys, which treat the Earth as a plane, the precise determination of the latitude and longitude of points over a broad area
       must take into account the actual shape of the Earth. To achieve the precision necessary for accurate location, the Earth cannot be assumed
       to be a sphere. Rather, the Earth's shape more closely approximates an ellipsoid (oblate spheroid): flattened at the poles and bulging at
       the Equator. Thus the Earth's shape, when cut through its polar axis, approximates an ellipse.  A "Datum" is a standard representation of
       shape and offset for coordinates, which includes an ellipsoid and an origin. You must consider the Datum when working with geospatial data,
       since data with two different Datum will not line up. The difference can be as much as a kilometer!

EXAMPLES

       A description of the available ellipsoids and sample usage of the conversion routines follows

   Ellipsoids
       The Ellipsoids available are as follows:

       1 Airy
       2 Australian National
       3 Bessel 1841
       4 Bessel 1841 (Nambia)
       5 Clarke 1866
       6 Clarke 1880
       7 Everest 1830 (India)
       8 Fischer 1960 (Mercury)
       9 Fischer 1968
       10 GRS 1967
       11 GRS 1980
       12 Helmert 1906
       13 Hough
       14 International
       15 Krassovsky
       16 Modified Airy
       17 Modified Everest
       18 Modified Fischer 1960
       19 South American 1969
       20 WGS 60
       21 WGS 66
       22 WGS-72
       23 WGS-84
       24 Everest 1830 (Malaysia)
       25 Everest 1956 (India)
       26 Everest 1964 (Malaysia and Singapore)
       27 Everest 1969 (Malaysia)
       28 Everest (Pakistan)
       29 Indonesian 1974

   ellipsoid_names
       The ellipsoids can be accessed using  ellipsoid_names. To store thes into an array you could use

	    my @names = ellipsoid_names;

   ellipsoid_info
       Ellipsoids may be called either by name, or number. To return the ellipsoid information, ( "official" name, equator radius and square
       eccentricity) you can use ellipsoid_info and specify a name. The specified name can be numeric (for compatibility reasons) or a more-or-
       less exact name. Any text between parentheses will be ignored.

	    my($name, $r, $sqecc) = ellipsoid_info 'wgs84';
	    my($name, $r, $sqecc) = ellipsoid_info 'WGS 84';
	    my($name, $r, $sqecc) = ellipsoid_info 'WGS-84';
	    my($name, $r, $sqecc) = ellipsoid_info 'WGS-84 (new specs)';
	    my($name, $r, $sqecc) = ellipsoid_info 23;

   latlon_to_utm
       Latitude values in the southern hemisphere should be supplied as negative values (e.g. 30 deg South will be -30). Similarly Longitude
       values West of the meridian should also be supplied as negative values. Both latitude and longitude should not be entered as deg,min,sec
       but as their decimal equivalent, e.g. 30 deg 12 min 22.432 sec should be entered as 30.2062311

       The ellipsoid value should correspond to one of the numbers above, e.g. to use WGS-84, the ellipsoid value should be 23

       For latitude  57deg 49min 59.000sec North
	   longitude 02deg 47min 20.226sec West

       using Clarke 1866 (Ellipsoid 5)

	    ($zone,$east,$north)=latlon_to_utm('clarke 1866',57.803055556,-2.788951667)

       returns

	    $zone  = 30V
	    $east  = 512543.777159849
	    $north = 6406592.20049111

   latlon_to_utm_force_zone
       On occasions, it is necessary to map a pair of (latitude, longitude) coordinates to a predefined zone. This function allows to select the
       projection zone as follows:

	    ($zone, $east, $north)=latlon_to_utm('international', $zone_number,
						 $latitude, $longitude)

       For instance, Spain territory goes over zones 29, 30 and 31 but sometimes it is convenient to use the projection corresponding to zone 30
       for all the country.

       Santiago de Compostela is at 42deg 52min 57.06sec North, 8deg 32min 28.70sec West

	   ($zone, $east, $norh)=latlon_to_utm('international',  42.882517, -8.541306)

       returns

	    $zone = 29T
	    $east = 537460.331
	    $north = 4747955.991

       but forcing the conversion to zone 30:

	   ($zone, $east, $norh)=latlon_to_utm_force_zone('international',
							  30, 42.882517, -8.541306)

       returns

	   $zone = 30T
	   $east = 47404.442
	   $north = 4762771.704

   utm_to_latlon
       Reversing the above example,

	    ($latitude,$longitude)=utm_to_latlon(5,'30V',512543.777159849,6406592.20049111)

       returns

	    $latitude  = 57.8030555601332
	    $longitude = -2.7889516669741

	    which equates to

	    latitude  57deg 49min 59.000sec North
	    longitude 02deg 47min 20.226sec West

   latlon_to_mgrs
       Latitude values in the southern hemisphere should be supplied as negative values (e.g. 30 deg South will be -30). Similarly Longitude
       values West of the meridian should also be supplied as negative values. Both latitude and longitude should not be entered as deg,min,sec
       but as their decimal equivalent, e.g. 30 deg 12 min 22.432 sec should be entered as 30.2062311

       The ellipsoid value should correspond to one of the numbers above, e.g. to use WGS-84, the ellipsoid value should be 23

       For latitude  57deg 49min 59.000sec North
	   longitude 02deg 47min 20.226sec West

       using WGS84 (Ellipsoid 23)

	    ($mgrs)=latlon_to_mgrs(23,57.8030590197684,-2.788956799)

       returns

	    $mgrs  = 30VWK1254306804

   mgrs_to_latlon
       Reversing the above example,

	    ($latitude,$longitude)=mgrs_to_latlon(23,'30VWK1254306804')

       returns

	    $latitude  = 57.8030590197684
	    $longitude = -2.788956799645

   mgrs_to_utm
	   Similarly it is possible to convert MGRS directly to UTM

	       ($zone,$easting,$northing)=mgrs_to_utm('30VWK1254306804')

	   returns

	       $zone = 30V
	       $easting = 512543
	       $northing = 6406804

   utm_to_mgrs
	   and the inverse converting from UTM yo MGRS is done as follows

	      ($mgrs)=utm_to_mgrs('30V',512543,6406804);

	   returns
	       $mgrs = 30VWK1254306804

AUTHOR

       Graham Crookham, grahamc@cpan.org

THANKS

       Thanks go to the following:

       Felipe Mendonca Pimenta for helping out with the Southern hemisphere testing.

       Michael Slater for discovering the Escape Q bug.

       Mark Overmeer for the ellipsoid_info routines and code review.

       Lok Yan for the >72deg. N bug.

       Salvador Fandino for the forced zone UTM and additional tests

       Matthias Lendholt for modifications to MGRS calculations

       Peder Stray for the short MGRS patch

COPYRIGHT

       Copyright (c) 2000,2002,2004,2007,2010 by Graham Crookham.  All rights reserved.

       This package is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

perl v5.10.1							    2010-06-13								  UTM(3pm)