True pressure

[MaxH]

Sorry guys, didn’t realize that you took it that serious. I even placed a (wink)smiley after the question. Or you must be a pilot and use it for navigation (joking!!)

Max

[par]

Bad news.

We must cancel this modification.

It turned out that we cannot reliably detect the pressure this way.
Some METAR stations provide pressure on the sea level, but some on the altitude of the place.
And there is no way to find this information.
For the time being YoWindow is going to display the pressure value received from METAR station.

A METAR station that provides the pressure from the altitude is in Drezden - EDDC.
http://en.allmetsat.com/metar-taf/europe.php?icao=EDDC

[Smith88]

Hi Pasha,

You don't have to cancel this function, because the METAR code contains the QNH value of pressure, where pressure is reduced to the sea level according to the ICAO standard atmosphere.
EDDC (Dresden) provides the sea-level pressure too. If it was the local pressure, the sea-level pressure should be almost 30 hPa higher, and it's nearly impossible.
In this table, P0 is the local, P is the sea-level pressure.
http://rp5.ru/Weather_archive_at_Dresde ... he_airport



Adrian

[par]

Wow, Adrian, thank you so much!

What would I do without our friends?

As soon as I find time I will try to explore this possibility.

[Mallorca]

Hi Pasha,

Adrian is right
The METAR information "Q" (in America "A") is allways the local station pressure adapted to the standard sea level pressure 1012 hPa.
Here an example of my PWS from today with the different views.

Projekt3.jpg (95.42 KiB) Viewed 10843 times

Werner

[par]

Thanks for additional info, Werner!

[par]

Friens, I think in case of Dresden the things go wrong.
This is the URL YoWindow takes METAR for Dresden from.
http://www.aviationweather.gov/adds/met ... n_ids=EDDC

Current response
EDDC 180450Z 06011KT 9999 -SG OVC013 M05/M08 Q1013 R04/190095 NOSIG

There are no QNH value, only Q- value (Q1013)

I need your help.
Do you think that Dresden METAR is an exceptional case?

Maybe a solution is to have a list of METAR stations that provide the pressure from the altitude?
But I wonder how much large this list is going to become...

[Mallorca]

Hi Pasha,

I think here is some confusion
All aviation Metars showing only the "Q" values (f.e. Sakt Petersburg http://www.aviationweather.gov/adds/met ... n_ids=ULLI)
Because the "Q" is the "QNH" http://en.wikipedia.org/wiki/QNH
QNH is one of the many Q codes and if the pilot is asking for the pressure he get the "Q" value and this is all over the world the pressure measured on the airport corrected to the sea level in this area. Otherwise it would be impossible to adjust the instruments on board.
This was one of the basics I had to learn to get my PPL (Private Pilot License) ....
Werner

[par]

Wow cool

Do you think Dresden METAR is an exception from this rule?
I mean that they provide the pressure incorrectly.

[Mallorca]

Hi Pasha,

why do you think that EDDC Dresden has incorrect values? Please have a look at the nearby stations http://www.checkwx.com/wxmain/code/EDDC
You will realize that it is only a minimum of 1 or 2 hPa difference.

Werner