Barometric Pressure

[Greenside]

If anyone has a fairly reliable barometer could they please PM me so I can get a reading at some convenient time. Thanks.

[Dustoff]

~

Current conditions, Chiangmai Airport

Trust the guys

Who fly the skies...

Edited June 25, 2009 by Dustoff

[rikki]

~

Current conditions, Chiangmai Airport

Trust the guys

Who fly the skies...

Can you tell me if I have to be at the same height as the airport to calibrate my altimeter/barometer using their data??

[Dustoff]

~

Current conditions, Chiangmai Airport

Trust the guys

Who fly the skies...

Can you tell me if I have to be at the same height as the airport to calibrate my altimeter/barometer using their data??

No.

It doesn't matter how tall you are (height);

Your elevation (i.e on a mountaintop);

Your altitude (as in an aircraft)..

If you are within a reasonable distance from the airport, say 50Km, the barometric pressure will be closer than you would care to question anyway. Assuming of course that you are setting an altimeter?

If not, check out this link

[rikki]

I want to calibrate my barometer/altimeter on the gps.

I believe I have to calibrate both because they are dependent on each other

thanks for the link, I'll look at it.

~

Current conditions, Chiangmai Airport

Trust the guys

Who fly the skies...

Can you tell me if I have to be at the same height as the airport to calibrate my altimeter/barometer using their data??

No.

It doesn't matter how tall you are (height);

Your elevation (i.e on a mountaintop);

Your altitude (as in an aircraft)..

If you are within a reasonable distance from the airport, say 50Km, the barometric pressure will be closer than you would care to question anyway. Assuming of course that you are setting an altimeter?

If not, check out this link

[Blinky Bill]

Your GPS altitude is calibrated on the GPS elipsoid, most likely WGS84.

[FarangFlyer]

Your GPS altitude is calibrated on the GPS elipsoid, most likely WGS84.

Pressure decreases with altitude. So it will make a difference if you are at a significantly different altitude from the weather station where you are taking your readings from. 30ft=1mb approx (27 is usually a bit closer to the truth in the sort of atmospheric conditions that we have in Thailand). This is why barometric pressure is normally given with reference to sea-level, and it is this that you would normally want to set when calibrating.

Within 30kms of the weather station, pressure should not change too much (on a calm day), unless you are around Lampang which for some reason seems to have quite different pressures from Chiang Mai (with the elevation difference removed of course).

By all means use a GPS fix to obtain your altitude, depending on the satellites, it is usually accurate to 100ft (or 3mb)

(WGS 84 Datum is solely for Lat/Long co-ordinate position)

If you fancied an adventure, you could always take your baro to the weather office at Chiang Mai Airport and set it up from there!

For more modern methods, most weather data can be displayed on your sidebar (Vista, Win 7) using the weather network gadget.

[FolkGuitar]

How about just going to the parking lot of the CM airport, and setting your altimeter to 340 meters (I believe that's the local height above sea level there. Better check that first. ) That should set your barometer spot on, wouldn't it?

[davidgtr]

Why not just go to the Met Station at the airport & get the info direct from the horses mouth in real time.

The Northern Region Meteorological station

N18 46.299 E98 58.158

Mahidol Road, left hand side after Customs & Immigration.

There's a line on the wall with the precise altitude so you can get it right + a barometer that they will read & so give you the exact barometric pressure then & there.

[cloudhopper]

Why not just go to the Met Station at the airport & get the info direct from the horses mouth in real time.

The Northern Region Meteorological station

N18 46.299 E98 58.158

Mahidol Road, left hand side after Customs & Immigration.

There's a line on the wall with the precise altitude so you can get it right + a barometer that they will read & so give you the exact barometric pressure then & there.

An altimeter set to a known elevation will also automatically read out the pressure setting (which normalizes local actual pressure at that altitude to sea level pressure). This is the pressure number given out by airports but will not be the same as shown on a regular barometer located above sea level.

[Greenside]

Sadly, after all this no doubt excellent advice it looks like the lads at Heathrow, Shanghai or BKK managed to render my new barometer inoperable en route from Blighty. Anyone suggest a place to get it fixed? I doubt Amorn would even know what it was

Edited July 20, 2009 by Greenside

[FarangFlyer]

Sadly, after all this no doubt excellent advice it looks like the lads at Heathrow, Shanghai or BKK managed to render my new barometer inoperable en route from Blighty. Anyone suggest a place to get it fixed? I doubt Amorn would even know what it was

An avionics engineer should be able to sort it properly. I may be flying out of Chiang Mai middle of next week. If I find one there, I will PM you contact details.

It may be that the aneroid capsules have been damaged though, in which case repair is probably not practical.