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[aprssig] Where is KT5TK-11?

Steve Dimse steve at dimse.com
Sun Feb 12 21:14:33 UTC 2012


Someone or something played old packets into the APRS IS. If you look at the raw data

http://www.findu.com/cgi-bin/raw.cgi?call=KT5TK-11&time=1

you can go back in time and see the telemetry and data packets match exactly, the repeats were dumped in over a period of just a couple minutes starting 1647z. Years there was a client, I forget which, that when a user played back a track on their screen it forwarded the packets to the APRS IS so everyone got to watch the playback. That was quickly identified and fixed. Either someone is running an old version or there is a new problem.

APRS, both on RF and the Internet is a real time system. Eleven years ago, when few home stations were connected to the Internet for solid NTP service system clocks were wildly inaccurate. After a week I stopped parsing timestamps completely, they caused far more problems than they solved. 

Apparently aprs.fi does some filtering based on timestamps, perhaps when built in timestamp is too great an error from realtime. Those packets should never have appeared on the APRS IS, and whoever sent them is the culprit. The question of ignoring or processing these packets would be a philosophical debate of epic proportions. I don't want to go there.

findU treats the APRS IS as the real-time system it was designed to be. If someone erroneously dumps old data onto the APRS IS it will be treated as live data, as all data on the APRS IS is designed to be. 

Anyone that watched the track of the balloon around 1647z should make sure their software is up to date.

Steve K4HG

On Feb 12, 2012, at 2:03 PM, Greg D wrote:

> Hi folks,
> 
> I'm confused.  Or, something is.
> 
> According to Findu, the balloon is over Dickinson Texas, last received 1 hr, 37 minutes ago.
> 
> According to aprs.fi, the balloon is off the Louisiana coast, last received some 10 hrs ago.
> 
> They can't both be right...  Probably neither is, but what's up with APRS-IS?
> 
> Greg  KO6TH
> 
> 
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