[aprssig] Google Maps on Cell Phones

Joel Maslak jmaslak-aprs at antelope.net
Tue Jan 8 01:29:48 EST 2008

On Jan 7, 2008, at 10:48 PM, Steve Noskowicz wrote:

>     Uh...  Correct me if I'm wrong, but If this was the case, a  
> moving tracker
> would give away it's location simply by using the center of the  
> circle.
> Actually, so would a stationary one if it was truely given a circle  
> shape.  And
> besides, this is much more math.  Truncation of lat/lon is a trivial
> "calculation".
>    As it is, the truncated-fix ambiguity does this to a much lesser  
> degree for
> a moving tracker as the square jumps when crossing the lat/lon lines.

If the tracker is using GPS, and wanting position ambiguity to hide  
it's location, I'd agree with you.

If he's using Loran (does that still exist?), celestrial navigation,  
cell phone tower loations, digipeater locations, etc, you might have  
a high precision but low accuracy location.  You shouldn't  
necessarily discard the low order digits but rather simply express  
the data you have with an uncertainty factor.

That's the problem -> there are two reasons you would want to use  
position ambiguity: 1) to hide where you are, but give limited info  
and 2) to express that you don't have a high accuracy GPS unit.   
Maybe even a third reason: 3) to express what area you are located in  
(an airport, for instance - maybe the airport sits on the corner of  
four of the rectanglish-ambiguity regions).

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