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[aprssig] Protocol parsing questions

J.C. Wren jcwren at jcwren.com
Thu Nov 20 21:19:20 UTC 2008


I'm getting back into APRS after a few years (oh, about 15, I think).  I'm
in the process of writing a ground-up Java parser, as my eventual goal is to
run a native application on the Android G1 that uses it as a position
reporting device.

I've run across a few packets that I can't determine the contents of based
on the 1.0.1 and 1.1 specifications.  For example, the packet below:

CCDES-1>APRSWX,WIDE1-1,WIDE2-2,qAR,W3AHL-4:@200150z3957.34N
/07535.07W_108/000g000t029r000p000P000h48b10170L000gt41.93vw0.243bv12.78fr000.C100

We have a 'g000' that says what the gust is.  Then we have a 'gt41...'  I
have no idea what that is.  There's also the question of when to stop
parsing, and treat the remainder as a comment.  In the 1.0.1 PDF file, a
number of the example weather packets are shown with 'wRSW'.  'w' should be
the software version, but it's not define in the list that follows.  Is
there a known sigil for deciding the remainder of the packet are comments?

I also see a number of improperly formatted packets hitting aprs-is.  Like
this one:

"WN0X-2>AP1WWX,KA0GFC-5,WIDE1,KB0WZI-3*,WIDE2-1,qAR,AC0JK-5:@200812z3837.76N
/09220.63W_014/00

Note the incomplete speed field.  What's the appropriate course of action?
Discard it?

Then there are these packets:

N1HQ>APS227,TCPIP*,qAC,THIRD:N/
N1HQ>APS227,TCPIP*,qAC,THIRD:08
N1HQ>APS227,TCPIP*,qAC,THIRD:54
N1HQ>APS227,TCPIP*,qAC,THIRD:0.

I'm guessing these might be a QSO or something, but I don't understand how
to programmatically identify them.

Can someone point me to some documentation i might be overlooking?  Or
provide some insight from experience?

Thanks,
--jc (K4JCW)
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