[aprssig] Compressed position + wx data

Matt Werner kb0kqa at gmail.com
Tue Mar 14 23:17:48 CST 2006

On 3/14/06, Curt Mills <archer at eskimo.com> wrote:
> On Tue, 14 Mar 2006, Matt Werner wrote:
> > Can someone tell me what could be wrong with this packet:
> >
> > 20060315030920,KB0KQA>APX181,DULUTH*,WIDE3-2,qAR,KA0TMW-1:
> > =/6d9G70,R_{;C322/000g000t017r000P000p000b10181XU2k
> Near as I can tell without digging out the spec it looks correct.
> You have the '=', a symbol table character, four lats, four longs, a
> symbol of '_' (weather), then 3 bytes at the end of the compressed
> position (didn't look to see if those are course/speed or something
> else, but three bytes there is correct).  After that comes the
> weather stuff and it looks correct to me.

The three bytes on the end are a PHG.  A HamHUD correctly decodes it
as a range of about 14 miles.  The HUD (and aprsworld) correctly
decode the position so I didn't figure that one out by hand - I
assumed it was correct.  The problem appears to be that the weather
stuff is not being decoded as wx.  It also appears that aprsworld also
doesn't decode the PHG value correctly.

> > Neither findu or aprsworld decode it correctly.  It shows up on
> > findu's error page.  Aprsworld decodes the position but interprets the
> > weather (and part of the compressed packet) as status.
> If you bring in the track data from findu for that station does it
> decode correctly in Xastir?

I didn't try that.  Xastir generated the packet you see above.  I will
try and do that later tonight or tomorrow.

My point here is that I want to generate some awareness for this type
of packet which is supported by xastir.  If the packet is correct by
the spec (which I guess I believe it is but I want to make sure), then
I'd like to see other software decode it correctly.

73 - Matt

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