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

Robert Bruninga bruninga at usna.edu
Mon Jun 5 12:35:44 UTC 2006


That is a failure of the display software to properly display
position ambiguity.   Software should never display an ICON
at a point other than where the sender intended.  If a station
is transmitting ambiguity, then the display software must
unequivocably convey that meaning to the viewer and -not-
simply placing the ICON somewhere else...

In the original APRS, depending on map Range Scale, a SYMBOL
is shown if the "size" of the symbol is larger than the area of
ambiguity.  But if the viewer zooms in below that point, then 
the symbol is replaced with a CIRCLE showing the size of the
ambiguity.  Thus, there is never any confusion on the part 
of the viewer as to what he is seeing and he will NEVER see
a symbol in the wrong position.

>I believe you need to set position ambiguity to off. 
>That feature ... allows you to specify how close to your actual 
>location you want reported to the network.

Not exactly.  Unfortunately that is the interpretation that results
from the improper implementation of the ambiguity concept that
we see in so many APRS clones.  Ambiguity simply means the
degree of precision to which the SENDER knows his position.
It should be honored and displayed on receipt as well.  Unfortunately, 
this is just another one of those fundamentals that has been left
out of so many APRS follow-on clones.   de WB4APR, Bob

>>  *From KF4PVT:*
>> *I am new to packet and APRS. ... on findu.com is appears about 
>>100 miles due north  of my actual location....
>> POS AMBIGU =4digits






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