> No, it's not possible that CoPilot is getting anything from the
> internet. When I'm using the device I'm in the car and have no wi-fi or
> cell connection.
Anytime that it is connected to the Internet it is either downloading
for checking the date on the Almanac. The Almanac is the database of
all the orbital and timing information for the constellation of GPS
satellites.
Cellphones have the additional benefit of knowing their general
position thanks to the position of the serving cell-tower.
Unfortunately, this isn't always correct if the antenna on the
cell-tower is a remote off of another tower because it thinks the
hosting tower, is the position, not the tower with the physical
antenna. Regardless, what it does do is get the device in the
neighborhood which vastly shortens the time to first fix. Then,
because the Almanac is already downloaded, this saves the three
minutes or so for the data to be received. The satellites broadcast
their own empheris about every 30 seconds, so from acquiring the first
satellite to getting basic positional information is no less than 30
seconds in most cases--depending on when in the cycle the the
acquiring begins.
Once a standard stand-alone GPS receiver has loaded the almanac, and
it isn't cold booted, the time to get position is usually quite short.
People who rarely use their GPS units or force cold boots on them will
complain because it always takes a long time for position acquisition.
Cellphones have the advantage of not only having the Almanac
downloaded into the device, but will either use the serving tower
position or its own last-known position. Some phones use the WiFi
location too.
The cell-tower triangulization feature is one of those "sometimes"
works features. Nice in theory, but highly impractical in most
circumstances. It really only works when the phone is in overlapping
coverage areas and there are no signal reflecting buildings nearby.
The signal hand-off from one tower to the next and load-balancing
features are nice, but rarely work as desired, so most carriers have
those features dumbed down a lot.
This last week, I ran into a problem with my carrier. We were in an
area that was supposed to have tremendous coverage. But it looked like
the wilt feature was enabled which greatly affected the service. Oh
well... Mice and Men.
AG
--
Ken Norton
ken@xxxxxxxxxxx
http://www.zone-10.com
--
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/
|