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CURTIS

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Walter Mankowski

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, <waltman@cpan.org>

COPYRIGHT AND LICENSE

Copyright 2003-2011 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.