[aprssig] Numerals Needed to Report Pressure

Robert Kirk isobar at bcpl.net
Tue Feb 28 11:36:34 EST 2006

Do it the way the meteorologists do;  you actually only need 3 numerals to 
report barometric pressure. No need to transmit the leading 9 or 10, and 
drop the decimal point, too. Thus, a pressure of 1024.7mb is coded as 247, 
and 992.6mb becomes 926.

There could be rare overlaps (central hurricane low pressures can go below 
940, for instance and Siberia/Canada can go above 1040 in the winter) , but 
context is obvious during analysis.

At 07:54 PM 2/18/06 -0500, Robert Bruninga wrote:
> >>> archer at eskimo.com 02/18/06 8:32 PM >>>
> >I just saw another bug this week from a UI-View
> >weather station that...  If the barometric pressure
> >is too low, UI-View sends 4 numerals in the field
> >instead of five.  Other clients don't decode
> >it because it isn't per the spec.
>Hummh...  I thought it was actually the other way around.
>No need to send the 1 when above 1000 mb because
>the only other thing it can be is in the 900's....
>I thought that was the way APRS does it.
>I assumed the spec does it that way too...
>Maybe I am remembering wrong.

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