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[aprssig] Mic-E Position Ambituity in APRS (Robert

Robert Bruninga bruninga at usna.edu
Tue Jan 8 19:16:58 UTC 2008


> Sorry, Bob, but what you describe is precisely 
> the definition of truncation.  If I truncate 
> something, I lop off a piece of it and leave 
> nothing behind. 

Wrong interpretation.  You have nothing to truncate or to lop
off.  If you only know a position as 3859 and no further
precision, then you are not lopping off anything.  You are only
transmitting what you have.

> The value "34.4567" truncated to two decimal 
> places is "34.45__".  Rounding is a different 
> story since I may change one of the digits.  
> But pure truncation is exactly what you've done.

No way.  If I had a position of 34.4567, then I would transmit
it.  There is nothing to truncate because there is nothing
missing.

> The application is going to insert not just zeros but
> a whole range of values to plot the result.

It should not insert or present precision that was not know by
the sender.

> If I've got "34.45__" then the full range 
> of values between 34.4500 to 34.4599 when 
> truncated result in the value you just 
> transmitted.

No you do not.  You do not have those range of values.  You only
have what the sender sent.  That is "34.45"  to suggest that is
the same as 34.4500 would fail middle school science.


Bob





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