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[aprssig] findu.com Location off by 100 miles.

Robert Bruninga bruninga at usna.edu
Tue Jun 6 02:52:18 UTC 2006


>> Ah, but again that interpretation is not interpreting the sender's
>> intent.  Position ambiguity means the sender is only sure of his
>> position to some level of accuracy.  If he uses 1 mile ambiguity
>> then it does not make sense to try to force precise "edges" of that
>> unknown quantity to something too precise.
>
>In this day and age this is a ridiculous statement. It is  
>particularly true with D7/00 poitions which are deliberately de- 
>precisioned.

Ah, Especially! in this day and age!  

We must not let computer programs force real-world data which 
includes levels of inprecision into perfectly little precise bits where 
the original information was not preceise in the first place.  Because 
once it is in the computer, it becomes as precise as the computer, 
yet it was -not- ever intended to be more precise than the original
data..

APRS was founded on this principle that the senders level of knowledge
about the accuracy of the information he is trying to convey is honored
and properly conveyed to the receipent.   No one likes to see things like
a bill from the Phone company that says you owe $34.2354778956321 .
Nor when the library sends you an overdue notice, that your book is
3.43125467 days overdue.

No, we try to teach kids in school that the way we present numbers 
conveys two things.  1) The magnitude of the value and  2)
the precision to which that quantity is known.  We do that by
how many digits of precision we include.

APRS was fundamentally based on that principle that the senders
position -and- his knowledge of the precision of that position would 
be conveyed to all viewers  to avoid any problems with missinterpretation.   
The lack of some software displays to convey the senders intended precision 
information undermines the integrity of APRS and causes problems
where there shouldnt be any.

We have been arguing this issue for over 9 years now, I really
wish you could figure out a way to convey the sender's intent 
(with respect to his precision (called ambiguity in APRS)) to
the recepient so we can get all these issues of missinterpretation
behind us.

Hope that helps...
Bob, WB4APR





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