NAME
Geo::Coordinates::DecimalDegrees - convert between
degrees/minutes/seconds and decimal degrees
SYNOPSIS
use Geo::Coordinates::DecimalDegrees;
(degrees, $minutes, $seconds, $sign) = decimal2dms($decimal_degrees);
(degrees, $minutes, $sign) = decimal2dm($decimal_degrees);
$decimal_degrees = dms2decimal($degrees, $minutes, $seconds);
$decimal_degrees = dm2decimal($degrees, $minutes);
DESCRIPTION
Latitudes and longitudes are most often presented in two common formats:
decimal degrees, and degrees, minutes and seconds. There are 60 minutes
in a degree, and 60 seconds in a minute. In decimal degrees, the minutes
and seconds are presented as a fractional number of degrees. For
example, 1 degree 30 minutes is 1.5 degrees, and 30 minutes 45 seconds
is 0.5125 degrees.
This module provides functions for converting between these two formats.
FUNCTIONS
This module provides the following functions, which are all exported by
default when you call "use Geo::Coordinates::DecimalDegrees;":
decimal2dms($decimal_degrees)
Converts a floating point number of degrees to the equivalent number
of degrees, minutes, and seconds, which are returned as a 3-element
list. Typically used as follows:
($degrees, $minutes, $seconds) = decimal2dms($decimal_degrees);
If $decimal_degrees is negative, only $degrees will be negative.
$minutes and $seconds will always be positive.
If $decimal_degrees is between 0 and -1, $degrees will be returned
as 0. If you need to know the sign in these cases, you can use this
longer version, where $sign is 1, 0, or -1 depending on whether
$decimal_degrees is positive, 0, or negative:
($degrees, $minutes, $seconds, $sign) = decimal2dms($decimal_degrees);
decimal2dm($decimal_degrees)
Converts a floating point number of degrees to the equivalent number
of degrees and minutes which are returned as a 2-element list.
Typically used as follows:
($degrees, $minutes) = decimal2dm($decimal_degrees);
If $decimal_degrees is negative, only $degrees will be negative.
$minutes will always be positive.
If $decimal_degrees is between 0 and -1, $degrees will be returned
as 0. If you need to know the sign in these cases, you can use this
longer version, where $sign is 1, 0, or -1 depending on whether
$decimal_degrees is positive, 0, or negative:
($degrees, $minutes, $sign) = decimal2dm($decimal_degrees);
dms2decimal($degrees, $minutes, $seconds)
Converts degrees, minutes, and seconds to the equivalent number of
decimal degrees:
$decimal_degrees = dms2decimal($degrees, $minutes, $seconds);
If $degrees is negative, then $decimal_degrees will also be
negative.
dm2decimal($degrees, $minutes)
Converts degrees and minutes to the equivalent number of decimal
degrees:
$decimal_degrees = dm2decimal($degrees, $minutes);
If $degrees is negative, then $decimal_degrees will also be
negative.
CAVEATS
The functions don't do any sanity checks on their arguments. If you have
a good reason to convert 61 minutes -101 seconds to decimal, go right
ahead.
AUTHOR
Walt Mankowski,
COPYRIGHT AND LICENSE
Copyright 2003-2007 by Walt Mankowski
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
THANKS
Thanks to Andy Lester for telling me about pod.t
Thanks to Paulie Pena IV for pointing out that I could remove a division
in decimal2dms().
Thanks to Tim Flohrer for reporting the bug in decimal2dms() and
decimal2dm() when $decimal_degrees is between 0 and -1.