NAME

Geo::METAR - Process aviation weather reports in the METAR format.

SYNOPSIS

  use Geo::METAR;
  use strict;

  my $m = new Geo::METAR;
  $m->metar("KFDY 251450Z 21012G21KT 8SM OVC065 04/M01 A3010 RMK 57014");
  print $m->dump;

  exit;

DESCRIPTION

METAR reports are available on-line, thanks to the National Weather Service. Since reading the METAR format isn't easy for non-pilots, these reports are relatively useles to the common man who just wants a quick glace at the weather. This module tries to parse the METAR reports so the data can be used to create readable weather reports and/or process the data in applications.

USAGE

How you might use this

Here is how you might use the Geo::METAR module.

One use that I have had for this module is to query the NWS METAR page (using the LWP modules) at http://weather.noaa.gov/cgi-bin/mgetmetar.pl?cccc=EHSB to get an up-to-date METAR. Then, I scan thru the output, looking for what looks like a METAR string (that's not hard in Perl). Oh, EHSB can be any site location code where there is a reporting station.

I then pass the METAR into this module and get the info I want. I can then update my webcam page with the current temperature, sky conditions, or whatnot. See for yourself at http://webcam.idefix.net/

See the BUGS section for a remark about multiple passes with the same Geo::METAR object.

Functions

The following functions are defined in the METAR module. Most of them are public, meaning that you're supposed to use them. Some are private, meaning that you're not supposed to use them -- but I won't stop you. Assume that functions are public unless otherwise documented.

metar()

metar() is the function to whwich you should pass a METAR string. It will take care of decomposing it into its component parts converting the units and so on.

Example: "$m->metar("KFDY 251450Z 21012G21KT 8SM OVC065 04/M01 A3010 RMK 57014");"

debug()

debug() toggles debugging messages. By default, debugging is turned off. Turn it on if you are developing METAR or having trouble with it.

debug() understands all of the folloing:

        Enable       Disable
        ------       -------
          1             0
        'yes'         'no'
        'on'          'off'

If you contact me for help, I'll likely ask you for some debugging output.

Example: "$m->debug(1);"

dump()

dump() will dump the internal data structure for the METAR in a semi-human readable format.

Example: "$m->dump;"

version()

version() will print out the current version.

Example: "print $m->version;"

_tokenize()

PRIVATE

Called internally to break the METAR into its component tokens.

_process()

PRIVATE

Used to make sense of the tokens found in _tokenize().

Variables

After you've called metar(), you'd probably like to get at the individual values for things like temperature, dew point, and so on. You do that by accessing individual variables via the METAR object.

This section lists those variables and what they represent.

If you call dump(), you'll find that it spits all of these out.

VERSION: The version of METAR.pm that you're using.
METAR: The actual, raw METAR.
TYPE: Report type in English ("Routine Weather Report" or "Special Weather Report")
SITE: 4-letter site code.
DATE: The date (just the day of the month) on which the report was issued.
TIME: The time at which the report was issued.
MOD: Modifier (AUTO/COR) if any.
WIND_DIR_ENG: The current wind direction in english (Southwest, East, North, etc.)
WIND_DIR_ABB: The current wind direction in abbreviated english (S, E, N, etc.)
WIND_DIR_DEG: The current wind direction in degrees.
WIND_KTS: The current wind speed in Knots.
WIND_MPH: The current wind speed in Miles Per Hour.
WIND_GUST_KTS: The current wind gusting speed in Knots.
WIND_GUST_MPH: The current wind gusting speed in Miles Per Hour.
WIND_VAR: The wind variation in English
WIND_VAR_1: The first wind variation direction
WIND_VAR_2: The second wind variation direction
VISIBILITY: Visibility information.
WIND: Wind information.
RUNWAY: Runway information.
WEATHER: Current weather (array)
WEATHER_LOG: Current weather log (array)
SKY: Current cloud cover (array)
TEMP_C: Temperature in Celsius.
TEMP_F: Temperature in Fahrenheit.
DEW_C: Dew point in Celsius.
DEW_F: Dew point in Fahrenheit.
HOURLY_TEMP_F: Hourly current temperature, fahrenheit
HOURLY_TEMP_C: Hourly current temperature, celcius
HOURLY_DEW_F: Hourly dewpoint, fahrenheit
HOURLY_DEW_C: Hourly dewpoint, celcius
ALT: Altimeter setting (barometric pressure).
REMARKS: Any remarks in the report.

NOTES

Test suite is small and incomplete. Needs work yet.

Older versions of this module were installed as "METAR" instaed of "Geo::METAR"

BUGS

The Geo::METAR is only initialized once, which means you'll get left-over crud in variables when you call the metar() function twice.

What is an invalid METAR in one country is a standard one in the next. The standard is interpreted and used by meteorologists all over the world, with local variations. This means there will always be METARs that will trip the parser.

TODO

There is a TODO file included in the Geo::METAR distribution listing the outstanding tasks that I or others have devised. Please check that list before you submit a bug report or request a new feture. It might already be on the TODO list.

AUTHORS AND COPYRIGHT

Geo::METAR is covered under the GNU Public License (GPL) version 2 or later.

The Geo::METAR Web site is located at:

  http://idefix.net/~koos/perl/Geo-METAR/

CREDITS

In addition to our work on Geo::METAR, We've received ideas, help, and patches from the following folks:

  * Ethan Dicks <ethan.dicks [at] gmail.com>

    Testing of Geo::METAR at the South Pole. Corrections and pointers
        to interesting cases to test.

  * Otterboy <jong [at] watchguard.com>

    Random script fixes and initial debugging help

  * Remi Lefebvre <remi [at] solaria.dhis.org>

    Debian packaging as libgeo-metar-perl.deb.

  * Mike Engelhart <mengelhart [at] earthtrip.com>

    Wind direction naming corrections.

  * Michael Starling <mstarling [at] logic.bm>

    Wind direction naming corrections.

  * Hans Einar Nielssen <hans.einar [at] nielssen.com>

    Wind direction naming corrections.

  * Nathan Neulinger <nneul [at] umr.edu>

    Lots of enhancements and corrections. Too many to list here.

RELATED PROJECTS

lcdproc at http://www.lcdproc.org/ uses Geo::METAR in lcdmetar.pl to display weather data on an lcd.