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[aprssig] Object Classification (FINAL WORD)

Bob Bruninga bruninga at usna.edu
Tue Oct 18 13:56:43 UTC 2011


Here is SUMARY on Objects, Staitons, and Tactical calls usage in APRS:

I have been very busy, so may not be following the thread and am leaving in
2 hours for 3 days travel.  But I will clarify exactly how APRS works with
respect to objects and stations and tactical calls.

1) Objects, Tactical calls and Stations all have one objective.  That is, to
send a SYMBOL and a POSITION and some comment data into the tactical
situational awareness of everyone involved.

2) All of these "things" no matter how they are transmitted should be
treated EXACTLY THE SAME once they are received.  They are "things" with
POSITION on an APRS map or data base.

3) The EQUALITY of these "things" was fundamental to the APRS design.
Because  the whole idea of an APRS map was to maintain a TACTICAL
SITUATIONAL AWARENESS in a distributed system architecture.  Meaning...

4) ANYONE with new, more relevant or updated information about ANYTHING on
the APRS map is allowed to update that "things" position, text, or comment,
and that UPDATE is propagated to all stations, and all maps, and so everyone
sees the same tactical picture updated in real time from live human
operators "maintaining the tactical picture".. And the person that did the
last update is KNOWN and CAPTURED.

5) THIS MEANS, an OBJECT, a STATION, or a TACTICAL CALLSIGN are IDENTICL
with respect to updates.  If the mobile WB4APR-9 is showing in the middle of
the bridge, because that was the last posit before my APRS device died, and
yet it was being used in an event and I am now elsewhere, I should be able
to go to ANY APRS station and update an OBEJCT of the same name WB4APR-9 and
that OBJECT should completely replace all instances of WB4APR-9 (the
station) on all maps and everywhere.  The idea is HUMANS maintaining the
*correct* tactical picture, not dependent on the garbage and errors
generated by devices, and a means so that the HUMANS can clean it up on the
air.

This on-air editing is FUNDAMENTAL to APRS.

***   The Problem is that UIVIEW DID IT WRONG ***  Uivew treats objects and
stations separately and thus crippled this fundamental aspect of APRS.  And
since 85% of APRS operators used UIview at one time or another, they
accepted this erroneous implementation as right.  But it is wrong.

SO, back to the difference between OBJECTS, STATIONS and TACTICAL CALLS.
THEY ARE ALL THE SAME.  They simply use different formats to transmit the
same POSITION data.

STATION FORMAT: lets the TNC MYCALL be the "thing's name".  This has the
advantage  that it saves 11 bytes, because the MYCALL is always in the
packet anyway.  It has the disadvantage that the "things" name can only be 6
alphanumericas and an SSID.

OBJECT FORMAT:  lets the NAME be up to 9 alphanumeric letters, and allows
for a time stamp.  Receiving stations are supposed to capture these to the
same POSITION list as everything else (replacing anything with the same
name, just like any other same-named thing).  Receiving systems are also
supposed to capture WHO sent the object as well.  Display of that is up to
the client.  ITEMS are the same as OBJECTS too

TACTICAL-CALLS FORMAT: is simply taking the STATION FORMAT and using a
TACTICAL name that will fit in the limitations of MYCALL field.  But to be
legal AX.25, this packet format needs to include the FCC callsign of the
sending station, and this is usually done by adding the TEXT of "de MYCALL"
within the text of the position report at the end.

The ONE ADVANTAGE OF USING THE STATION FORMAT, is that only the STATION
FORMAT can be forced through the APRS-IS and through an IGATE back to RF as
a courtesy position report WHEN-AND-ONLY-WHEN that station is involved in
2-way messaging.

So, in the case of Lynn's Satellite Objects, it is a perfect marriage, of
using a TACTICAL CALL of the name of the satellite so that his global server
system gets this ADVANTAGE of the courtesy posit that can go back through
the IGate to someone requesting info on said satellite.  Hence, the logical
way to identify his program as the SOURCE of these TACTICAL CALLS is by
doing what we have always done for tactical calls, that is PUT "de KJ4ERJ"
at the end of the packet.

Hope that clarifies it all.

Bob, Wb4APR




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