[aprssig] MultiLine Weather Object parsing

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Wed Feb 23 12:34:22 EST 2011

I'm having trouble decoding a MultiLine weather object from WXSVR-AU, 
specifically the following (Skip half way down for my actual question):


According to what I understand from 
http://www.aprs-is.net/WX/MultilineProtocol.aspx and 
http://www.aprs-is.net/wx/, this breaks down as:

Product: BFU
Object: CWS0515zA which is:
     CWA: CWS
     ttttz (issue time): 0515z
     Line number: A
DDHHMMz (expiration time): 250515z
Lat/Lon is obvious and symbol is /: or Fire.
Sequence: N5FAA which is:
     DHM: N5F (Day 23, Hour 5, Minute 16
     Uniqueness: AA

All of this makes sense (except for the off-by-one-minute issue times), 
but it's inside the MultiLine that I'm having trouble.


appears to be missing the first character indicating the type of the 
line which should range from a to l (lower L) (at least, according to 
http://www.aprs-is.net/WX/MultilineProtocol.aspx that's what's supposed 
to come first).

If I ignore that, then:

0 = Closed Polygon
5 = Scale
followed by 6 lat/lon offsets of DE BR NW YX PL DE

So, is it safe to say that if the first character is not a through l, 
then the line type is not specified and interpret the remainder if the 
lengths and such make sense?  It's actually my "length must be odd" 
check that's stopping my parser at this point, but that's just as well 
because 0 is an undefined line type.

Is there any other APRS client application that actually interprets and 
displays MultiLine objects like these?

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

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