[aprssig] APRS SPEC: Wind Speed confusion

Greg Trasuk trasukg at trasuk.com
Fri Oct 14 10:33:10 CDT 2016

Unless there’s a compelling reason otherwise, I’d standardize on knots, to correspond with both aviation and marine weather reports.  Anyone that looks at either of those regularly will be thrown off by mph, I would think.


Greg Trasuk, VA3TSK

> On Oct 14, 2016, at 10:47 AM, Robert Bruninga <bruninga at usna.edu> wrote:
> 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?
> Bob, WB4APR
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