[aprssig] APRS resolution and symbols

[Scott Miller]

> 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...

That's why it's a hierarchy.  Like your HUMAN symbol, for example - one 
code can represent a human, and a sub-code can represent a skier, 
another a jogger, and so on.  If a new sub-code gets added that you 
don't know, you can still display the symbol for human and not be wrong.

As long as the hierarchy is structured right, it also helps you with 
filtering what you want to see - for example, in the current taxonomy, 
you could easily separate ground equipment from air units from weather 
symbols.  See MIL-STD-2525B for the system that inspired it.

Scott
N1VG