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[aprssig] APRS resolution and symbols

Robert Bruninga bruninga at usna.edu
Tue Oct 2 00:24:49 UTC 2007


>> The OpenTRAC spec already gives you something 
>> like 2 cm resolution...
>
> Can the two share 144.390 with a gradual changeover? 
> That eventually leaves a lot of APRS users with 
> hardware... and software that would become obsolete. 

Things move pretty slowly.  WIDEn-N came out in 1998, 10 years
ago, and look at how long it is taking to get HAMS to change
from RELAY and WIDE...  Throwing out all backwards compatibility
to 30,000 users so that a few people who can have GPS resoultion
to 2 centimeters but who then cannot be seen by any one else,
just undermines APRS communications integrity.  When the whole
point of APRS is to promote consistent information
communications between users.  The APRS spec does contain
resolution to 1 foot that IS backwards compatible to ALL 30,000
users.  No need to re-invent the wheel...

> Case in point... OpenTRAC will have an almost 
> unlimited ability to add more symbols. APRS has 
> only a handful of unused symbols. 

Not true.  Adding the symbol-a-week guarantees a loss in
communications integrity when not everyone has the new symbol
sets every-week.  As a case in point, it seems to take YEARS for
most clients to implement a changed SYMBOL set even when we only
add a few per year!  Imagine how impossible it would be to
communicate if all clients had to keep up with the new symbol
table of the week...

Back in 1996 we increased APRS from one symbol byte (91 symbols)
to two bytes yielding over 3200 potential symbols.  At that time
there were 700 defined, but WinAPRS wanted no more because each
additional one required special coding.  This summer, APRS1.2
(which the new Kenwoods have already adopted) is expanding the
use of that symbol set.  Just a month ago, we defined a new
symbol "O-" for OPERATOR PRESENT.

> Every mobile APRS user not in a vehicle, 
> aircraft, on horseback or in a wheelchair is a 
> jogger... none are standing still, walking, 
> skiing, hiking or whatever.

And every time you bring this up, I tell you that the only
reason that HUMAN symbol was initially called a JOGGER was
because in APRSdos, the only menu key I had at the time (1997)
was "J".  And back then I was trying to keep an association
between each letter of the alphabet and each symbol for easy
entry.  But that was 10 years ago.  Now selections are not made
by name any more!  So it is not a jogger, it is a human figure.

If you look at the SYMBOL definitions, you will see that the
symbol is named HUMAN.  And I still hold back on wasting symbol
sets for trying to define such meaningless differentiations
between  Standing, Walking or Hiking HUMANS!  How is the SKIER
with a tracker and an HT going to change his symbol from a SKIER
to a HIKER or to a WALKER each time he takes his skiis off, or
changes from boots to shoes?

To satisfy your complaints about the skier symbol, I have now
added the symbol "S[" as a skier, so that we don't have to
re-hear this complaint every winter...  How many years will it
be now until ALL software authors implement it?  And not until
all of them do, will you have any assurance that what you send
wille be displayed as intended.

Bob, Wb4APR





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