At 6:45 PM +0200 2005-07-19, Mikael Abrahamsson wrote:
I think the ground based radio transmitters needed for indoor operation
isn't around much outside the US. I was very surprised when I got a
cellphone-based GPS navigator from AVIS last time I was in the US, and
it started working inside the terminal building.
I had one of those, too. It was a Nextel phone. However, I
don't believe those use actual GPS signals. I believe those are
actually using triangulation from the cell phone towers (e.g., Time
Difference of Arrival, Angle of Arrival, and/or Enhanced Observed
Time Difference). They aren't as accurate as GPS, but they will give
you reasonably accurate position information anywhere you can get a
decent cell phone signal.
I have heard about new highly accurate/low-cost single-chip
clocks that would help improve accuracy of cell phone tower
triangulation, and would hopefully also be something that could be
put in standard desktop and laptop computers, making it much easier
to run software such as NTP to keep the system clocks much closer to
the correct time.
--
Brad Knowles, <[EMAIL PROTECTED]>
"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."
-- Benjamin Franklin (1706-1790), reply of the Pennsylvania
Assembly to the Governor, November 11, 1755
SAGE member since 1995. See <http://www.sage.org/> for more info.
