[aprssig] Weather Station Path/Rate Recommendations

Robert Bruninga bruninga at usna.edu
Tue Jan 20 17:35:41 EST 2009

> 1. Weather stations based on rapid change 
> sounds hard. You have temp, rainfall, 
> humidity, wind speed, wind direction, 
> barometer, and maybe dew point.  

Its actually easy.  The code simply checks the ASCII packet.  If
the packet is identical to the last packet sent, then there was
no change (though you mask out the WIND direction) from that
STRING comparison.  Done.

> 2. Wind Direction is notorious for rapid changes,

Which is why the original algorithm masks that field out of the

> 3. Most weather stations use a data averaging routine..

Doesn't matter, if the actual PACKET that goes out is identical
(except for wind direction ) from the last one, then it is
UNCHANGING data and should be delayed to save channel bandwidth.

> 4. ...my weather station use[s] a faster rate 
> of about 10 or 15 minutes in the spring & 
> summer... then ...20 minutes in the fall & 
> winter...  

If all APRS software implemented the basic decay rate for old
duplicate data and rapid refresh for new or changed date, then
there wouldn't be any user settings to depend on.  And
consistent performance from all stations year 'round.  And
independence from bad user settings.

> 5. As for paths, I suggest that is a local 
> thing to be worked out among the local 
> APRS sysops.... the weather service 
> specifically asked me to change my path to 
> do a 3 hop path so my data was visible on 
> the APRS station in the NWS office.    

Fine, but use a 'directed' WIDE2-1,DIGI2,DIGI3 path.

> I got flack for it from people living way 
> out of state,...

As expected.  There is no reason to flood several states and add
a factor 12 QRM (total copies 36) on the network with an abusive
FLOODING WIDE3-3 path in all directions when the correct
response to that request would have been a directed 3 hop path
to that NWS station.  Total copies 3 (while still serving ALL
stations within 1 hop and along the main route to the NWS..

>> 30 minutes is too slow for most situations. ...
>> for other types of weather ...rates of five 
>> minutes are desired by many ...
> Sounds obvious to me.  This suggests a Wx station "Smart 
> Beacon" algorithm.  Wx condition change rate handled just 
> like vehicle speed.
> No change -> 30 min _or more_
> Rapid change -> 5 min.
> 73, Steve, K9DCI 

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