[Xastir] Question about APRS GPS position precision

[Tom Russo]

On Sun, Oct 07, 2007 at 10:09:42AM -0700, we recorded a bogon-computron collision of the <archer at eskimo.com> flavor, containing:
> 
> Bob Bruninga came up with yet another method of adding precision,
> called DAO.  With this method you add some extra characters to the
> comment field that give you the extra precision _and_ specify the
> datum for the posit.  Very few APRS clients have implemented DAO at
> this time.  Bob likes it because it doesn't make the Kenwood radios
> obsolete I think.  As I recall the Kenwoods can handle Base-91 just
> fine for posits, but have a problem with Base-91 "Objects" or maybe
> it was just Base-91 "Items".

The kenwood D7&D700 don't understand Items at all, and can't deal with base-91
objects.  They handle base-91 posits Just Fine.  I don't quite understand why
they'd do that in the firmware --- if they're going to bother writing code
to handle base-91, why not let it apply to all types of position reports?  But
there you have it.  I don't know if the D710 supports base-91 fully.  Since 
Bob is so down on base-91 now and he had Kenwood's ear, I suppose not.

The big advantage of DAO is that stations that don't understand it just ignore 
the extra digits of precision it offers, and treat the packet as a regular 
un-compressed posit.

There are numerous statements flying around in APRSSIG that Xastir supports
DAO, but as far as I can tell this is incorrect, and Xastir knows nothing
about DAO.

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236 AHTB#1 http://kevan.org/brain.cgi?DDTNM
"And, isn't sanity really just a one-trick pony anyway? I mean all you get is
 one trick, rational thinking, but when you're good and crazy, oooh, oooh,
 oooh, the sky is the limit!"  --- The Tick