phpweather-devel

Problem when there's no dew-point

[Tom M. <to...@un...>]

Hello

PHPWeather doesn't seem to like Leeds Bradford Airport's (EGNM) metar
reports at the moment. Since about 14:00 GMT on Friday they stopped
including the dew point temperature on the metars.

Eg.

2003/06/14 11:50
EGNM 141150Z 12005KT 040V210 9999 FEW038 SCT080 18/// Q1023

The "18///" bit. The 18 represents the temperature, but there should be
another figure in place of the last two "//".

PHPWeather doesn't like this. I can understand it not returning a value for
dew point, but it doesn't return a value for the temperature either. It just
ignores all temperature readings.

I assume that Leeds Bradford Airport are returning their metar reports in
the wrong format, and should just be returning "18/" if they are not
including dew point rather than "18///".

Any ideas?

Tom

Re: Problem when there's no dew-point

[Nick B <nic...@ya...>]

Tom McDonald wrote:

>I assume that Leeds Bradford Airport are returning their metar reports in
>the wrong format, and should just be returning "18/" if they are not
>including dew point rather than "18///".
>
>  
>
Thats the correct format Tom. The UK METAR coding rules say that if dew 
point is not available the it should be replaced by a double ellipsis 
"//". I must have a word with my friends in ATC Engineering there and 
ask them to fix it ;-)


To quote from UK AIP GEN 3.5.10:
 ----snip----
9 Air Temperature/Dewpoint
9.1 These are given in Degrees Celsius, M indicates a negative value .
       Examples 10/03, 01/M01.

       If the dew point is missing, the temperature would be reported as 
10///
----unsnip----

If anyone would like access to the UK AIP you can register for free at  
http://www.ais.org.uk/  . Publications are available in PDF format.

Regards,
Nick B.

Re: Problem when there's no dew-point

[Tom M. <to...@un...>]

Ahhhh I see. So it's a bug with PHPWeather's handling of the METAR feed.
Interesting that the UK have different METAR coding rules than everyone
else. You'd have expected ICAO to have standardised it all. Though I guess
getting everyone to agree on something might be a tad optimistic ;)

Thanks for the reply, anyway.

Tom

> From: Nick B <nic...@ya...>
> Date: Sat, 14 Jun 2003 16:48:49 +0100
> To: php...@li...
> Subject: Re: Problem when there's no dew-point
> 
> Tom McDonald wrote:
> 
>> I assume that Leeds Bradford Airport are returning their metar reports in
>> the wrong format, and should just be returning "18/" if they are not
>> including dew point rather than "18///".
>> 
>>  
>> 
> Thats the correct format Tom. The UK METAR coding rules say that if dew
> point is not available the it should be replaced by a double ellipsis
> "//". I must have a word with my friends in ATC Engineering there and
> ask them to fix it ;-)
> 
> 
> To quote from UK AIP GEN 3.5.10:
> ----snip----
> 9 Air Temperature/Dewpoint
> 9.1 These are given in Degrees Celsius, M indicates a negative value .
>      Examples 10/03, 01/M01.
> 
>      If the dew point is missing, the temperature would be reported as
> 10///
> ----unsnip----
> 
> If anyone would like access to the UK AIP you can register for free at
> http://www.ais.org.uk/  . Publications are available in PDF format.
> 
> Regards,
> Nick B.
> 
> 
> 
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Re: Problem when there's no dew-point

[Martin G. <gim...@gi...>]

Tom McDonald <to...@un...> writes:

> Ahhhh I see. So it's a bug with PHPWeather's handling of the METAR feed.

Oh no, a bug?! :-) I believe I've fixed this now with this very simple
fix around line 447 in phpweather.php:

-      } elseif (ereg('^(M?[0-9]{2})/(M?[0-9]{2})?$', $part, $regs)) {
+      } elseif (ereg('^(M?[0-9]{2})/(M?[0-9]{2}|//)?$', $part, $regs)) {

...

-        if (!empty($regs[2])) {
+        if (!empty($regs[2]) && $regs[2] != '//') {

It simply makes the 'xx///'-case the same as the 'xx/'-case that
PhpWeather already handles.

> Interesting that the UK have different METAR coding rules than
> everyone else. You'd have expected ICAO to have standardised it
> all. Though I guess getting everyone to agree on something might be
> a tad optimistic ;)

Yes, this doesn't make things any easier for projects like this
one... Thanks (to both of you) for pointing this out.

-- 
Martin Geisler                       My GnuPG Key: 0xF7F6B57B

See http://gimpster.com/ and http://phpweather.net/ for:
PHP Weather:   Shows the current weather on your webpage and
PHP Shell:     A telnet-connection (almost :-) in a PHP page.

Re: Problem when there's no dew-point

[Nick B <nic...@ya...>]

>>interesting that the UK have different METAR coding rules than
>>everyone else. You'd have expected ICAO to have standardised it
>>all. Though I guess getting everyone to agree on something might be
>>a tad optimistic ;)
>>    
>>
I just checked the on-line FMH-1, the US version but as it is 1995 it 
may well have been updated.
I've also got some information on Canadian reporting, but thats in the 
office. Will check in a few days time.

>Yes, this doesn't make things any easier for projects like this
>one... Thanks (to both of you) for pointing this out.
>
>  
>
Thanks Martin, if  anyone wants to check, EGNM is still without dewpoint.

I've also got my own perl script that decodes metars at 
http://www.nowindows.net/cms/wxstuff.php
(Must tidy it up and release it for public consumption sometime.)

Nick.