[aprssig] APRS resolution

[Robert Bruninga]

> So at a glance it makes sense to have aprs resolution 
> go to 2 meters....  The aprs protocol should allow 
> me to place objects at a level of precision far below 
> what an ordinary GPS can provide. 

And APRS can do it with the !DAO! protocol for those that need
it.

> I use the machine readable derivation of the APRS !DAO!
> format when I convert garmin rino positions to aprs 
> objects using my script for xastir. 

Neat.  Glad to hear someone is using the APRS higher precision
format where needed.  But those that demand more digits in their
position reports need to be very careful...  Most maps are no
where near that resolution, and so relying on just more digits
gives many a false sense of precision.  But it does have merit
as long as both the sender and viewer are using the same map.
Then accuracy does not matter, but precision does.

That is why the APRS !DAO! Format identifies the DATUM used, in
addition to the extra precision...

Bob