[aprssig] APRS SPEC: Wind Speed confusion

Robert Bruninga bruninga at usna.edu
Fri Oct 14 09:47:09 CDT 2016


The APRS spec is confusing and uses WIND SPEED in Knots in some places and
in MPH in others.  This has been with us from the beginning.  But with more
and more code being put into hardware and not easily upgraded software,
should we fix this?

I think many existing radios and clients just decode them all as if they
were MPH anyway (metric countries convert MPH to KPH, or do they convert
KTS to KPH?)

* Raw Weather Report
* Positionless Weather Report ( ccccssssggggttttrrrrppppPPPPhhhbbbbbb )
* Complete Weather Report ( DIR/SPDggggtttttrrrrppppPPPPhhhbbbbbb )

* Storm Data (DIR/SPD/ST/www^GGG/ppp>RRR&rrr%ggg

ssss = sustained one-minute wind speed (in mph).
gggg = gust (peak wind speed in mph in the last 5 minutes).
SPD = the speed is expressed in knots.

www = Sustained wind in knots

GGG = Gust wind in knots

Should we change it to all MPH to get rid of this potential for confusion,
or will we just create more?

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