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[aprssig] barometric pressure units

Andrew P. andrewemt at hotmail.com
Mon Nov 5 03:36:08 UTC 2012


That's what I said. They are reporting in pascals, not in 10s of pascals (i.e., drop the units digit).  For example, if W3HOA-2 was reporting in 10ths of hectopascals, the value would have been 01016 (assuming rounding), not 10156. If you look at page 64 of the APRS 1.0.1 specification, it says (I quote):

b = barometric pressure (in tenths of millibars/tenths of hPascal).

So, what's going on? Has the protocol spec changed since 1.0.1 and I haven't found the change notice yet? Or has there been a de-facto change and the spec hasn't been updated to account for it?

Andrew Pavlin, KA2DDO

> From: steve at dimse.com
> Date: Sun, 4 Nov 2012 22:18:37 -0500
> To: aprssig at tapr.org
> Subject: Re: [aprssig] barometric pressure units
> 
> 
> On Nov 4, 2012, at 9:47 PM, Andrew P. wrote:
> 
> > But, even so, _no_ station in my area is reporting in 10s of pascals, as specified by APRS 1.0.1.
> 
> Sure?
> 
> http://www.findu.com/cgi-bin/wxnear.cgi?call=KA2DDO
> 
> closest station is 
> 
> http://www.findu.com/cgi-bin/raw.cgi?call=EW0301
> 
> presently reporting 
> 
> EW0301>APRS,TCPXX*,qAX,CWOP-3:!4002.66N/07527.34W_319/002g010t042r000P000p000L000h62b10150.VWS-DavisVP2+
> 
> The baro pressure is 5 digits following lower case b, or 10150, which sure looks like Pa / 10 (or hPa x 10) to me.
> 
> next closest is W3HOA-2, reporting 10156
> 
> In fact, of the 20 closest, the only one with data that appears bad is N3NTP-2.
> 
> Steve K4HG
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