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

Robert Bruninga bruninga at usna.edu
Tue Jun 6 03:15:31 UTC 2006


>>> steve at dimse.com 06/05/06 10:01 PM >>>
>> Again, position ambiguity is not for the purpose of masking or
>> hiding one's position.  It is for the purpose of reporting things
>> who's position is not precise.
>
>99% of the time (as in the case that started the thread) the  
>"culprit" is a D7/00 with a GPS input. You told Kenwood to implement  
>this feature whose result is to obfuscate a precise position.

No, Kenwood implemented position ambiguity as best they could
to honor the principles of APRS and not imply precision where
precision is not intended.  The intent in the D7 and D700 this is
for manually entered positions like I do all the time with my D7.
I agree, that it does not make a lot of sense to use a GPS with 
precison down to a few feet and then also transmit ambiguity bits
saying it is not precise.  But that is not for the recepient to decide. 
The sender chooses how to set up what he wants to send.

THe receepient should always display what the sender sends.
If the recepient or the sender does not like it, then go back
to the sender and suggest he do something different.  But
we cannot maintiain the integrity of APRS if some systems
make imprecise positions into -wrong- precise positions on
receipt.

>Regardless, things like Google Maps have no concept of ambiguity.  

No, but applications that use those maps should.  There should be
a clever way to work around this.  I have already suggested the
simplest is to not zoom to a range scale below where the ambiguity
does not make sense or would cause confusion.

>Even if I considered your actions a good thing, it simply does not  
>translate into the modern world of internet mapping. 

I think one needs to step back and think "outside the box"...

>One must assign  a specific lat/lon to obtain a plot. 

OK, get the plot and then use some clever trick to indicate to the
viewer that the sender is transmitting a certain degree of ambiguity.
Write in big bold letters.  "POSITION IS AMBIGUOUS TO X miles"
if you must.  Or do not even display the map below the scale
where the ambiguity is say 10% of the size of the map.  I can
think of all kinds of ways to convey the meaning to the viewer.

> The world has moved on to "I'm  right here", your concept of 
>"I'm somewhere over here" is so 20th  century ;-)

Ah,... but that is what is wrong today in the 21st century.
COmputers try to force all the analog world into precision
where sometimes precision does not exist.  Think the location
of a thunderstorm...   These computers think the world should 
change  to match their little bits for ease in programming....   
I think, however, It is time for computers to start better 
reflecting what the human intended, not drawing lines in the 
sand (or on maps).

APRS was designed to convey to the recepient just what the
sender intended.  I am sure with a little ingenuity, that maps
of any kind can somehow convey this meaning to the viewer.
After all, it is the 21st century and we should be able to get
a computer to do it.

Thanks
Bob, WB4APR






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