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[aprssig] Dead Reckoning in APRS

VE7GDH ve7gdh at rac.ca
Sun Jun 18 22:03:17 UTC 2006


Bob WB4APR wrote...

> Well,  you must be a very busy person.  In our area with
> say over 70 mobiles on the map in the local area at any
> given time, you must have to do an awful lot of "hovering"
> to get the real tactical picture of what is going on. I prefer
> to see in an instant, at a glance, the entire picture.

I'm a very busy person, but not because I'm looking at 70 mobiles all of the
time. I'm not interested in ALL of the stations that I see on my screen. For
the most part those stations on the screen come and go, sit stationary or
move and so on. I occasionally concentrate on a particular station that I'm
interested in. If I'm really interested, I track that station. All the rest
are "just there" and I either ignore them or watch them. Believe me... if
the tools I was using didn't do what I needed them to do, I would use
different tools. I think the operative word there is "I"...  I use tools
that satisfy my needs. You use tools that satisfy your needs.

> APRS was designed for emergency use to facilitate
> communications and maintaining the local tactical
> situation to all viewers. I cannot imagine trying to
> use a system that required the operator to click on
> each of say 250 objects (the Wash DC area) on the
> map to see the most important attributes necessary for
> maintaning tactical situational awareness.

Are you really interested in ALL 250 objects? Now YOU must be a very busy
guy. I'm just an "APRS user" out of many. I would have to classify my use as
pretty casual. If there was a disaster taking place, the situation might
change. Regardless of whether it was just another day in Paradise or if some
other situation was unwinding, I would never be interested in or watching
"250 objects" at the same time. I would only be concerned in stations that I
could help or who could help me, my family or my neighbours. Every situation
would be different, but I just can't envision ME needing to watch every
single station that appeared on my screen.

> I fear you are still missinterpreting what "dead reckoning"
> means in APRS.  It is not and never was an intention
> to display a "position". I say again, the display is to show
> to the casual observer (without clicking) the passage
> of time and distance since that station was last heard.

I don't think I am misinterpreting anything... at least not now.  Up until a
day or two back, I thought that "dead reckoning" could have caused some
confusion. You explained the way it works in APRSdos very well a few
messages back. Up until a day or so back, I thought that dead reckoning
could have displayed an imprecise location. Your explanation was very clear.
It shows a "last position heard' and projects a vector from that last
position. Seems reasonable to me. Nice feature if you want it enabled.

> Abd I say, APRS viewers should be able to see at-a-glance
> the tactical situation without having to click around
> on the map.
>
> I designed APRS with all of the tactical display fundamentals
> that exist in some of the most modern military combat
> systems.  I served 20 years as a communication/combat
> system engineer in the Navy and my last 3 years were as
> the US Navy's "Senior Combat System Insepctor" for all new
> construction ships.  In that capacity, I was responsible
> for thoroughly testing the combat system and accepting
> or faulting the combat system on all new construction
> Aircraft Carriers, AEGIS class Cruisers and DD-51
> class destroyers.

It just goes to show you that no matter how good those systems are, things
can fall apart with mis-communication or lack of communication. The systems
may work, but human error or decisions can degrade the decisions made as a
result of the technology that is available, but we are digressing from APRS.
After all, it's not the fault of the pilot if friendlies on the ground
aren't identified on his screen.

> Believe me, the Navy knows how to present real-time
> information (including ambiguity), latency and all manner
> of attributes, and it does not require the operator to
> go around clicking on the hundreds of targets that may
> be attacking him.

You may not believe me, but I typed my last paragraph before reading your
paragraph above! My reference was to the four Canadian soldiers that killed
by "friendly fire" in Afghanistan when they were bombed while taking place
in an exercise a year or so back. I think that was a case where it might
have been worthwhile clicking on the screen and waiting for feedback about
the "flashes" they were seeing on the ground. Their display just showed them
the information that was available. The friendlies on the ground
unfortunately lacked the hardware that would have told the pilots of their
location. It was more a case of "lack of technology" and "lack of
communications" than of mis-interpreting what was on their screen. The
Canadian forces simply didn't exist on their screen so the pilots assumed
the flashes on the ground were "enemy forces" with deadly results.

> APRS provides for all these capabilities to display in
> real-time, all the information the viewers need to see
> to be able to fully comprehend the tacctical situation
> at a glance. It is too bad that many APRS clients
> other than the original left out many of these features.

I don't think that anyone is saying that there are features in APRSdos that
aren't useful. They are just voting with their feet in choosing what
software they are using. The way to end conversations like these is for
someone to write software that includes everything you are talking about. If
the users want features that aren't in APRSdos, or if they want other
mapping options or capabilities, then it's up to them. I'm not a programmer.
I'm a user. I can think up features that I would like to have, but I'm not
going to create that program. I'm reliant on others to do that.

> Be careful about comparing arm-chair casual APRS observing
> with what it was designed for, and that is tactical real-time
> display for busy operators with other communications
> responsibilities while operating under stress.

I think you are confusing APRS with the kind of systems you developed for 20
years in the military. There, one person might ultimately decide which
hardware and software will be used. In APRS, we have lots of choices.
Programs will come and go. When there is a compelling reason to move from
one program to another, users will do it. There's a big difference between
APRS and the way amateur radio operators use it and the military. I have
operated as SAR under pressure, but unfortunately before the odds'n'ends 
that we now use for APRS was available. The best I could do then was 
download a track when the GPS receiver returned to the EOC. That didn't stop 
me from dreaming about seeing teams in the field in real time. I haven't 
been involved in SAR for several years, so don't know if my team has have 
upgraded their capability since I was there. I still operate under stress, 
but I call that work & APRS doesn't play a part in that. Anyway, enough of 
this. I've got some catching up to do with work, so I'm going to have to 
drop out of this discussion. I will remain for the most part a casual APRS 
observer though!

73 es cul - Keith VE7GDH
--
"I may be lost, but I know exactly where I am!"





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