Pressure: local station vs. sea level

Hello all!

I would like to raise a topic on which I can not really balance the pros and cons. I obviously want to talk about the use of either local pressures or pressures brought down to sea level.

What I know/understand/intuite is:

Local pressure is what is measured by the probe. So I’m using it in all computation (as the computation must be done 1/ at the altitude where the pressure is measured and 2/ with temperature, humidity, etc. at the same location). I’m using it in data exchange too (always sending local pressures, hoping that the pressures that come from other systems are indeed local pressures too).

Sea level pressure is a computation (it’s rather an approximation, should I say). It’s mainly used in displaying because it’s easier to compare with normal pressure (which is a sea-level pressure, 1013.25 hPa).

But why the hell so many systems have different ways to handle this?
I saw smart aps displaying station pressure, software exporting only sea-level pressure, etc.

Do you know if there’s a “standard” on this? And you, how do you handle this?

Thanks for your future answers, my goal is not to tell whether a particular software is better or worst. I only want to compare your different approaches and the assumptions you have to make.

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Here’s the explanation of the three different reading types from a weewx perspective:,-pressure,-and-altimeter

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local pressure, unless adjusted for altitude, is just an altimeter reading
(i.e the higher you are , the lower it is)
and so to compare to anyone else’s reading, you need to have a common standard, which is adjusted to sea level pressure
There is though also a QNH barometer reading, which is used in airports and that takes into account not only your altitude but your air temperature (and an average at that) and humidity
but that reading needs to be computed knowing the raw un adjusted for altitude reading
also that reading is only different to a simple offset to adjust for altitude (to get sea level pressure) when you live at high altitude, eg above 5000 ft, e.g in say Denver Colorado


Awesome feedback as always gentlemen . . . :+1:

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Local pressure (or “station pressure”) is important because it is used for all sorts of other calculations . . . and . . . it is the only pressure you can calibrate your instruments for using a trusty old mercury barometer or some other trusted instrument. It is really hard to argue with a mercury barometer, but few people have them (ok, I have one).

But, as @weather-display says:

Hope this helps.



actually the station pressure is not important for the weather unless you want to boiling water, because station pressure affected by the force of the gravity on the air at specific place not as the sea level pressure that take the elevation and temperature into account to be useful for the weather. so we can know if my location have low pressure or high pressure by using SLP, as @weather-display said, you can get a very low pressure(station pressure) on the top of mountain.