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[aprssig] APRS return to basics (DR) (new images)

Bob Bruninga bruninga at usna.edu
Wed May 23 18:27:55 UTC 2012

Dead Reckoning:

I have added my recent CSE/SPD leader and Dead-Reckoning notes and some
sketched images to my SYMBOLS web page:

For those systems that do not display these fundamental features, please
consider it, it really fills in the original dimensions of APRS for moving

Bob, WB4aPR

-----Original Message-----
Sent: Sunday, May 20, 2012 5:07 PM
Subject: APRS return to basics (DR)

Dead dogs on the road.

I always look forward to the APRS travel day to Dayton, but get so
frustrated that it is nothing like it was 15 years ago before we got swamped
with fixed ICONS instead of moving symbols.  Now we just have these ICONS on
maps that have no CSE/SPD headers and that do not move, no matter how old
they are, like dead dogs on the highway.

I was using a client with full color APRS symbols and perfect maps and found
it was practically useless to find someone while moving.  You see a callsign
come into view and don't know if is there now, or something left from 3
hours ago!  You pass the spot on the road and it is like every other spot on
the road, nothing there... 

The original APRS dead-reckoned (DR'ed) all symbols.  That is, if they were
moving when they transmitted then APRS moved it on receipt until updated.
It gave REAL-TIME knowledge as to what was happening, not some pretty map
with 90% of all info not only out-of-date, but not even indicating what is
fresh and what is old dogs...  

Back with the original APRS, If someone was 1/4 mile ahead of you, then his
SYMBOL kept moving on your display the same 1/4 mile ahead of you (though
still dragging an anchor line back to a tiny circle showing when that was
updated).  This was a fundamental concept of APRS that went out the window
when we started just slapping fixed ICONS on windows or google maps.

I know some software has dead reckoning, so I am not complaining about them,
but if you are not seeing everything MOVING on your display, then you are
not seeing LIVE APRS.  I guess I am going to look deeper at what clients
bypassed this fundamental part of APRS.

Im thinking of a new way to suggest implementation.  That is, maybe only DR
for 10 minutes, and paint a DR'd symbol a light blue.  If the position
(which had CSE and SPD) has not updated in 10 minutes (2 attempts for a 5
minute commuter) then his symbol changes to GREY, and no longer a full color
symbol and is not DR'd..  As usual, if it is older than 80 minutes, then it
should disappear unless called for.

This will make it instantly visible what is really happening on APRS with
respect to moving stations. But the color, and the anchor circle and line
back to last reported position gives no one a false impression of where
someone was last reported and how much time has elapsed since that knowledge
was true.

We MUST make sure that all software at least has CSE/SPD leaders (showing
the direction and speed).  The length of the leader is proportional to the
log of speed so that 600 MPH aircraft have about a 2" leader and someone
walking at 3 MPH has a leader at least as wide as his symbol.

I need to go check the COMPATIBILITY tables and make sure that all APRS
clients do have leaders and DR.  If not, expect to hear from me.


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