Re: APRS positions not uploading to APRS.FI


Lynn Deffenbaugh
 

From https://aprs.fi/doc/guide/aprsfi-info-pages.html

Stations heard by X, and stations which heard Y

aprs.fi collects monthly summaries of digipeater and igate statistics. The info page shows both a table of digipeaters and igates which heard the given station, and (if the station is a digipeater or igate) which other stations where heard by that station. The most recently updated entries are shown using a larger font.

These statistics are usually somewhat correct, but there are several caveats, and as you've probably heard – there are lies, damn lies, and statistics.

  • The APRS-IS network that feeds the APRS packets from the igates to aprs.fi does duplicate suppression. Only the first gated copy of a packet traverses the entire network. All other duplicate copies seen within 30 seconds after the first packet are dropped by APRS-IS. A packet which is heard by multiple igates normally gets credited only for a single igate.
  • A lot of digipeaters do not add their own callsign in the packet's path when retransmitting a packet. aprs.fi cannot possibly know about those.
  • A lot of digipeaters do callsign substitution instead of insertion, replacing original path components. A packet with a path of OH7RDÖ,WIDE2-1 could have been a WIDE1-1,WIDE2-1 packet in the first place, and gone through OH7RDÖ and another unknown digipeater.
  • The aprs.fi "first heard" algorithm tries to go on the safe side: if it's not sure, it doesn't count as directly heard. But even then, some incorrect overly long paths are shown.
  • Stations transmitting invalid or fake coordinates will skew these statistics. If the transmitting station claims to be 1000 km away (due to a bad GPS fix), my best guess can only be that the station actually is that far away.
  • Items and objects are not shown here, since they are usually far away from the transmitter which transmitted the packets.
Read through that quote and I suspect that most of the packets you're copying are either a) injecting directly to the APRS-IS causing your RF receptions to be dupe-suppressed or b) have a path that causes aprs.fi to have doubts about the reception based on the above description.

The APRS-IS,  from which aprs.fi draws its data, is not usable for doing any sort of RF network analysis like "Stations heard by".  Although aprs.fi does make an attempt at it, it cannot be relied on as being complete.

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


On 1/31/2021 3:28 PM, macclad44@... wrote:
Hi, although  my raw packets are being reported by APRS.FI, and that I'm active, positions and stations that have clearly been decoded on my RF port are suddenly not being shown under "Stations heard by N7TTQ-9" nor "Stations which heard N7TTQ-9".  Identical stations heard identically up to the 29th were fine, then nothing.  I must have hit a button somewhere.  Mind you prop has not been good in the last few days but for example VA6ATA-1 I clearly have heard and have even messaged but doesn't show up as being heard by me nor vice versa.  

Does anybody have any ideas?

Thanks.
Jeff

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