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[aprssig] [ui-view] APRS Radiation sensor

Heikki Hannikainen hessu at hes.iki.fi
Sat Mar 26 11:46:25 UTC 2011


On Fri, 25 Mar 2011, Bernard Van Haecke wrote:

> Making it mandatory to use a special symbol (or one of a set of special symbols)
> for an APRS packet to be interpreted in one or another way may seem redundant.
> The weather report strings already adhere to a specific format.

Since the spec says so, the Ham::APRS::FAP parser only parses weather data 
from position packets having the WX symbol (and the positionless weather 
formats, too, which don't include symbols). So that's what aprs.fi does.

On the other hand, it won't look for other APRS data extensions (course, 
speed, altitude, DAO...) from the weather packets.

This reduces the chances of erroneous parsing of corrupted packets, and 
speeds up the parsing a bit, too.

> Should the use of a specific symbol be mandatory or just optional?

I don't see a need to change the spec.

> I.e. what if a balloon carries a simple or elaborate weather station 
> (with just a thermometer or a radioactivity sensor)?  can they still use 
> the balloon icon AND use the weather report format?  how about small 
> boats, camping tents, space shuttles :-) ?  They all have their icons. 
>  It would be nice if they can still use their more meaningful icon 
> regardless of their packet payload, whether it's weather data or 
> other things.

I suppose weather stations should be stationary, with sensors positioned 
according to some specifications. Not near buildings, no temperature 
sensors in direct sunlight, and so on, to make the readings reliable. The 
temperature sensors in cars, tents, boats are likely to be affected by the 
placement.

Also, the weather reports are supposed to be measured at ground level. If 
you send a balloon and transmit high-altitude weather reports, they'll 
just confuse everyone and their weather forecast software, since it's much 
colder and more windy up there.

> Do sites like aprs.fi only show weather charts when the /_ symbol is 
> used?  I think it would be interesting to know.  I hope they don't and 
> they look at the packet payload instead.

aprs.fi does this according to the specification, ie. checks the 
symbol.

   - Hessu


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