GIS: How to read METAR & TAF values to get the pressure at sea level?

I have this link on how to get the altitude in Android -> SensorManager.getAltitude(pressure at sea level, atmospheric pressure)

But... need to know the value for PRESSURE AT SEA LEVEL. I have read the below statement from Android documentation on how to obtain it.

The pressure at sea level must be known, usually it can be retrieved from airport databases in the vicinity.

Then, I found url that may give the values by providing the airport code. In my case, it's Tokyo International Airport (Haneda). The airport code is HND.

Here's the web service provider url: http://avdata.geekpilot.net/

Here's the sample output for Tokyo International Airport (http://avdata.geekpilot.net/weather/HND)

<weather>
<ident>RJTT</ident>
<error/>
<metar>
2011/09/22 08:00
RJTT 220800Z 04019KT 9999 开发者_如何学编程-SHRA FEW012 BKN025 BKN040 21/18 Q1000 NOSIG
</metar>
<taf>
2011/09/22 04:12
TAF 
      AMD TAF 
      AMD RJTT 220409Z 2204/2306 08016KT 9999 FEW030 SCT050 
      BECMG 2204/2206 05014KT 
      TEMPO 2207/2209 36018G30KT SHRA 
      BECMG 2303/2306 10008KT
</taf>
</weather>

Problem: don't know on how to read the above information to obtain the value.

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METAR altimeter (sea level pressure) data are usually presented as A2992 or ALTSG 2992 where 29.92 is the value in in. Hg or at airports using millibars as Q1000 as in your example, which is exactly 1 atmosphere or bar.

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I found url to translate obtain it and translate it to readable format.

find local sea level pressure

My airport code there is RJTT (Tokyo International Airport Haneda)

Here's the sample output (Pressure (altimeter): 30.21 inches Hg (1023.0 mb)):

METAR text:      RJTT 260100Z 03011KT 9999 FEW025 BKN110 BKN170 20/14 Q1023 NOSIG RMK 1CU025 6AC110 7AC170 A3021
Conditions at:  RJTT (TOKYO INTL AIRPO, JP) observed 0100 UTC 26 September 2011
Temperature:    20.0°C (68°F)
Dewpoint:   14.0°C (57°F) [RH = 68%]
Pressure (altimeter):   30.21 inches Hg (1023.0 mb)
Winds:  from the NNE (30 degrees) at 13 MPH (11 knots; 5.7 m/s)
Visibility:     6 or more miles (10+ km)
Ceiling:    11000 feet AGL
Clouds:     few clouds at 2500 feet AGL
broken clouds at 11000 feet AGL
broken clouds at 17000 feet AGL
Weather:    no significant weather observed at this time