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My tracker is giving erroneous results

MS19087

Well Known Member
I am wondering if the ground station software has changed . . . my last 2 tracks are showing bad data - my flight was 35 minutes and it is showing results over 2 hours . . . check out this link . . . http://mail2600.com/cgi-bin/track.cgi?call=N91RV&start=2013-08-05 13:12:38&stop=2013-08-05 21:12:38

This track from yesterday is showing strange results too - looks like i doubled back - which i have not - seems to point to delays on ground side with reporting my position etc.
http://mail2600.com/cgi-bin/track.cgi?call=N91RV&start=2013-08-04 14:35:46&stop=2013-08-04 22:35:46


Any ideas??
 
Last edited:
Hi Mark,

The default for most APRS messages is to use the receive/relay station time as the timestamp of a message. If a station is slow to relay a message it's easy for a few messages to get out of sequence. For us it looks like you airplane jumped forward and backward.

Check out this post ...

http://www.vansairforce.com/community/showthread.php?t=75260

It describes a configuration that addresses "most" timestamp related track errors.

I should add that it's still possible for tracks to have messages out of sequence. The above solution is implemented by the website developers and is not a general solution for delayed messages.

If you follow Sam's instructions and still see errors in your message timestamps, check you track on both mail2600 and aprs.fi to see if the latter is able to clean up the errors.
 
Thanks glen

This is exactly how I am setup. Did it back in 2011. It has operated perfect until this weekend ...
 

Not exactly. The last three packets are shown in the correct location but their timestamp is after 1600 UTC and your takeoff was after 1300 UTC. I also think there are a quantity of good packets that have been discarded and some that are duplicated but they aren't noticed in the flight path when the "dots are connected" by the straight line.

The problem is caused by the WA3NOA igate delaying your packets by about 2 hours. (!)

Just about every packet igated by WA3NOA is delayed and that screws up the "bad packet filter algorithm" at aprs.fi and at mail2600.com (my site) -- but in different ways, each with its own advantages and disadvantages.

FYI, the APRS-IS looks back 30 seconds to filter duplicate packets. mail2600.com looks back an additional 55 minutes. In the case of WA3NOA, a 3-hour lookback seems necessary (with an attendant increase in processing <sigh>). I'm probably not going to implement it but if it continues to be a problem I'll add that callsign to my filter list to ignore.

The right solution is to work with the errant igate station to fix the problem at its root cause but it often feels like a game of whack-a-mole :-(

--
Joe
 
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