I've developed a NWS CAP protocol parser to inject local weather events
into APRS.  In doing so, I spent much time researching the required
format of such a message.

I found detailed comments in alert.c.  I also found a document from
WB4APR (http://www.aprs.org/APRS-docs/WX.TXT) that was updated in 2010.
 There is documentation on http://www.aprs-is.net/wx/ that shows how
they format their Weather Alert packets and may represent the current
best practice.

The three sources of info don't completely align.

Comments in alert.c indicate that the "title" in received packets
should include an underscore between the state and the zone, i.e.

Packets generated via WE7U and AE5PL omit the underscore.  That is what
Xastir actually seems to require, as it adds the underscore itself.  If
the underscore is included, Xastir adds a 2nd and the display in the Wx
Alert window does not work properly.

I am also trying to clarify whether the underscores between multiple
words in the "alert_tag" are required.  Xastir comments state, "You
must ignore anything after a space in the alert." WB4APR says the
"type" is free text.  Xastir doesn't actually seem to care and my
generated alerts look nicer without the underscores.  But WE7U does use

Thought: Perhaps WE7U's data source includes underscores where the CAP
atom feed does not.   I see that WE7U is one of the primary developers,
so please chime in.

Nor does Xastir seem to care if there is a trailing comma (as specified
by WB4APR) after the last "title" element or a space between the last
"title" and the "{zcs" value.

Perhaps the comments are out of sync with the current reality and could
be clarified by someone who fully understands the code as implemented? 
This could be quite useful.

The NWS CAP protocol (http://www.nws.noaa.gov/directives/sym/pd01017003
curr.pdf) has defined the following "Significance" values:

W - Warning
A - Watch
Y - Advisory
S - Statement
F - Forecast
O - Outlook
N - Synopsis

Xastir already handles Warning, Watch, and Advisory.  I would find it
useful, and therefore suggest/request, that the alert_entry.to
values be expanded to conform with the NWS CAP possibilities and to add
STMNT, 4CAST, OUTLK, and SYNOP to the list of values.

Thanks for any comments and your consideration.


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