[aprssig] Barometric pressure compensation

Mark Williams kf6yu at cox.net
Wed Oct 21 15:38:21 EDT 2009

Hi Scott.

Maybe it's overly simplistic but I wait for  the pressure gradients to be 
minimal across the region and adjust the reading to agree with others in the 
area.  That's essentially what Peet recommends in their setup procedure. 
Actually, I added the pressure gradient part as my station is remote and not 
near any NWS sources.  Let's call this the "secondary standard" approach.


----- Original Message ----- 
From: "Scott Miller" <scott at opentrac.org>
To: "TAPR APRS Mailing List" <aprssig at tapr.org>
Sent: Monday, October 19, 2009 2:38 PM
Subject: [aprssig] Barometric pressure compensation

> I'm making good progress on my APRS weather station kit, but I've run into 
> a minor snag.
> To be useful, the station barometric pressure reading has to be reduced to 
> sea level.  This means making an estimate based on a fictitious layer of 
> air between the station and sea level, and that estimate makes assumptions 
> about the temperature and lapse rate in that layer.
> The NWS has an official algorithm for this, but it'd be rather tricky to 
> implement in a low-cost station.  The other amateur stations I can find 
> information on (uWeather, Hobby Boards) seem to have simple offsets with 
> no temperature compensation, which seems a little too simplistic.
> Among professional stations like those by Davis and Peet Bros, is there 
> any standard for how the sea level reduction is calculated?  Or do we just 
> assume that we're not going to get any meaningful data about horizontal 
> pressure gradients from home stations and only look at one station at a 
> time?
> Scott
> N1VG
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