ChairmanOfTheBored said:
Dumbfuck. Cellphones keep their last good reading and that gets
reported if a polled reading is not being reported by the phone.
Amazing. I guess it would then be trivial to display the Lat-Long on
the cell phone without the assistance of a for-pay location service.
Too bad there are only a few phones capeable of doing this. It seems
that to get location information, you have to subscribe to a server
based service. For example, Qualcomm has gpsOne, which has OPTIONAL
locally calculated position reports.
<
http://www.cdmatech.com/products/gpsone.jsp>
There are 4 different modes that it can operate. See:
<
http://www.cdmatech.com/download_library/pdf/gpsone.pdf>
<
http://www.snaptrack.com/technology/index.jsp>
To the best of my knowledge, only the "Mobile-Assisted" mode has been
implimented in deliverable handsets. Incidentally, Snaptrack is now
owned by Qualcomm.
Bullshit. The CELL PHONE takes a reading, and that is what gets
reported. ACTUAL COORDINATES, not some delay degraded data stream, you
retarded twit.
Nope. See:
<
http://www.gpsworld.com/gpsworld/article/articleDetail.jsp?id=12287>
"There are three basic types of data that the assistance server
provides to the GPS receiver: precise GPS satellite orbit and
clock information; initial position and time estimate; and for
AGPS-only receivers, satellite selection, range, and range-rate
information. The assistance server is also able to compute
position solutions, leaving the GPS receiver with the sole job
of collecting range measurements."
"Collecting range measurements" means satellite delays.
A bit on a location server:
All vehicles are "shielded" to a certain degree, idiot. It all depends
on where one places one's GPS antenna.
I've seen some measurements with various cellular handsets for GPS
signal strength and quality under various conditions. Sitting on your
belt or purse, while inside a vehicle, is actually fairly usable if
you want to take long samples. Indoors, in a forest, or in an urban
canyon full of reflections, GPS signal quality is really awful.
Fortunately, the typical operating position and user location for
talking to the cell tower, is also usually an adequate location for
obtaining a location fix. With the aquisition time reduction provided
by A-GPS, it can be done without draining the battery.
It is a constant operation of the phone, and has a
specific update period.
Nope. For normal E911 only operation, the receiver is powered off
until the PSAP requests a fix. The location server provides the
necessary to initialization data, the handset provides the satellite
delays, the location server chews on everything and provides the PSAP
with location data. It then turns off the GPS section until the next
request.
SiRF GPS chips currently are down to about 250mw of power consumption.
It takes about 1-2 seconds for an A-GPS initialization and an average
of about 15 seconds to obtain a fix sufficient to meet FCC's accuracy
specs. That won't kill a handset battery if used sparingly, but will
rapidly deplete the typical handset battery if used for continuous
tracking. Older implementations are not so efficient. Some sucked as
much as 1 watt.
When are you going to stop making shit up? Cell phones have had GPS
capacity for over three years now, and they have most certainly tackled
any power consumption issues.
Sure, mostly because it's not being used much and then only if polled.
However, you're correct that current GPS chips are far less power
hungry and have a faster TTFF (time to first fix) than older handsets.
As long as these modes of operation are being used, there's no power
problem. However, if you're planning on tracking someone
continuously, or polling excessively, as in advertiser supported LBS
(location based services), you'll probably have a signifigant effect
on battery life.
Not where... WHEN, and the WHEN is not as often as you would like to
claim, dingledorf. If one can get a call indoors, one can be tracked to
their location indoors. The GPS poll will merely report the last valid
reading taken, and the cell tower triangulation will verify it, or
correct for any difference from it.
Amazing. How does a single cell tower triangulate a handset position?
I thought it takes 3 to tango err... triangulate.
Incidentally, I live in a mountain forest, where GPS satellite
visibility is rather poor. I just put my Samsung SCH-i700 into
service mode to display the GPS data. Zilch. No birds in view. My
Verizon XV6700 showed blank fields for GPS data, which means either no
satellites or I screwed up somewhere (i.e. forgot to enable GPS
receiver). I'll try it again when I go to my palatial office in a few
days. Anyway, if you have a cell phone handy (does not need to be
activated), with a GPS, I can probably find the magic test mode code
so you can see for yourself what is being sent and whether it will
work indoors at your location.