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[aprssig] Re: The best resolution of position from APRS

Robert Bruninga bruninga at usna.edu
Wed Jan 4 05:45:03 UTC 2006


>>> kc2mmi at verizon.net 01/03/06 11:59 PM >>>
>How is a D7 going to decode what NMEA format to give 
>6" position rsolution, when the display physically is only 
>doing DDD.MM.mm due to the available display digits?

It is going to display it the same way it always has.
Whereas it wont display ANYTHING if someone uses
the high precision obsolete compressed object format.

Which would you rather have?   
a) Nothing  (XASTIR sending the obsolete compressed object format
or
b) at least as good as you always had?   

That is the debate.

Now, you say, but you want the precision down to
6" on your D7?  What on earth are you going to do
with it?   

>I'm confused by your "new" position spec, I don't find 
>any definitions of your DD.MM.HH format.   What are 
>the H's for? 

DD is degrees.  MM is minutes and HH is hundredths of
a minute.  

>And do you mean, a human has to manually translate the 
>DD.MM format and then manually add the other digits, 
>to the lat/lon displayed? It sounds like an inelegant kludge, 
>if that is being forced on the human operator in order to 
>accomodate the Kenwood limitations. 

You are not understanding it.

1) When XASTIR sends a compressed object NO ONE USING
A KENWOOD WILL SEE IT.  That is the problem.  They
will not even know the object exists.  It is invisible to
10,000 users of kenwoods.  This is bad for APRS it
is bad for communications when people do not see
what is on the air and do not even know what they
are not seeing.

2) But, When anyone who must have 1 foot resolution for
objects sends the new APRS 1.2 !DAO! format, everyone
including all kenwoods and any old software they may have
lying around WILL SEE the object the same way they always 
have.  But those softwares that support the !DAO! and
the users that require that accuracy will see the object to 
the exact foot too.  Plus they will see what datum is
used by the sending station.

In other words, #1 is broken and can never be fixed.
Whereas #2 is 100% compatible witih everything out
there, does not  break anything, and those people
who must have 1foot resolution can have it.  Done.

de Wb4APR, Bob





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