[OZAPRS] WXSVR-AU CWA Duplicates and missed bits

[Geoff]

Hi Tony,

Yep - I see the duplication in FLI and will fix that up with the next
shapefile release....  Thanks :-)

Regarding messages, yes they ARE truncated but sent as separate parts.
(see http://wxsvr.aprs.net.au/protocol.html for full details)

Basically each warning consists of an area message, object (optional), and
plain-text message.  Each beacon for the same message has the same 4
character sequence information (last 5 chars in each message following {,
looks like  {P7iAA )

The fifth character is an overall sequence character, allowing the operator
to reassemble the parts in order (or find the missing parts in your case)

Here's an example from yesterday's onslaught:

RIVSTS>APRS:;RIV_STS  *280810z3445.42S\14534.44ETSevere Tstorm {S57AA
RIVSTS>APRS::NWS_WARN :280810z,TSTORM,NSZ55 {S57AB
RIVSTS>APRS::BOMRIV   :SEVERE THUNDERSTORM WARNING FOR (LARGE HAIL, FLASH
FLOODING  {S57AC
RIVSTS>APRS::BOMRIV   :AND DAMAGING WINDS) FOR THE ACT AND ALL NSW
DISTRICTS,  {S57AD
RIVSTS>APRS::BOMRIV   :EXCEPT SYDNEY. {S57AE

Here we see an object (packet A), Area message (packet B) and message
(packets C, D and E)

It could also be if there are multiple areas coming out of your gate, and if
your gate does limiting of the RF (If you are using UI-View it is known to
drop packets)

If you think there should be a second part to a message but it doesn't
arrive, you can check the Query page at http://wxsvr.aprs.net.au/query.php
Select your CWA and PID, check the APRS box and see what the server
generated. If the server is missing the additional parts, I can investigate
further.

Cheers,
Geoff  XJG


-----Original Message-----
From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On
Behalf Of Tony Hunt
Sent: Friday, 28 November 2008 11:28 PM
To: OZ-APRS Mial-list
Subject: [OZAPRS] WXSVR-AU CWA Duplicates and missed bits

I saw a bit of a problem today. Early in the day we had some thunderstorms
pass through in the Wakefield MDN and Flinders FLI and these gated fine out
to RF onto the D700 ..

Currently I am Gating a few CWA zones that I probably would not normally.
These are just beyond the normal limits of the network. It helps give an
idea of how this NWS stuff  works.

Problem. Later in the day we got a set of Alerts messages etc came through
for TAS onto RF. East of  Flinders Island by the looks of it.. Its easy to
see how, as it seems there are duplicate CWA codes for VK7 and VK5 .. Check
the FLI CWA codes on this page.
http://wxsvr.aprs.net.au/zones.php

Not sure how to get around this one but I thought it was worth a mention..
I am not likely to Gate FLI stuff normally but the VK7 boys might also find
it painful getting messages for VK5 FLI stuff which covers a large area.

Also we had some messages come through for some nearby areas and the last
bit of Text was cut off giving relavant locality info. It said something
like "Strong winds for people in areas " and then that was the end of the
message. It looks like it was beyond the size limit of a APRS message . With
all the Zone Time and preceding data slapped on it , it became a sizable
string. Seems a pity to get the warning and then miss the relavant locality
alltogether.

Once again I dont know what could solve this one but perhaps trunkating it
into a separate new APRS message as a continuation of the first one so to
speak. As with all APRS messages theres no guarantee which order they are
going to appear on a given network but perhaps a slight delay before the
continuation of the first to the second message being injected into the IS
might fudge it.

Its an interesting system for sure and a bit of a learning curve but we are
actually getting stuff working that looks like it could be useful .

Thanks Geoff

Tony Hunt VK5AH


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