While you can do cell sector positioning, usually the positions from
such systems are too inaccurate. There are a lot of factors that can
affect signal strength such as multi-path distortion, which is why
most carriers are moving to the assisted GPS for more accurate
location. In the US, all carriers are moving to assisted GPS to meet
the FCC mandate for emergence call positioning. The requirement is
location within 50 meters of actual position.
There are other satellite based systems out there, and there are also
systems that use other signals. For example, Rosum has a system that
uses terrestrial broadcast television signals to very accurately
determine location, even within buildings. In this system, a set of
receivers at known location
As a side note, in the 1950s and early 1960s, the Department of
Defense in the US had a plan where in the event of an attack from the
Soviet Union, radio stations and television stations would vary their
transmitter power so as to throw off the aim of incoming missiles an
bombers.
Eric Hildum
eric.hildum@mobileplay.com
On Nov 7, 2005, at 3:23 AM, Shannon Jacobs wrote:
>> From: "Mr. Eric Hildum" <EricHildum@earthlink.net>
>> Date: Thu, 3 Nov 2005 10:13:27 -0800
>>
> <snip>
>> A few phones are capable of autonomous GPS, and can do all the
>> calculations internally, but usually the assisted mode is so much
>> more accurate and much faster there is rarely a reason to use this
>> mode.
>
> This is only part of your very informative reply, for which I think
> you. Is
> there any way to determine if the Sanyo W22SA is one of the phones
> capable
> of autonomous GPS, and if so, how to enable it for that mode? It
> wouldn't
> actually be very useful because you'd need to have a separate map with
> latitude and longitude. Too much of a nuisance for driving, but
> perhaps
> useful if you want to go camping or boating. Or I guess it would be
> nice for
> marking the photos, too.
>
> From your description of the process, I'm not clear why they really
> need the
> satellite part at all. It would seem they could do pretty much the
> same
> thing by just working from the known locations of the cell towers
> and a
> comparison of the relative signal strengths of the nearest ones. That
> approach would seem to save quite a bit of circuitry.
>
>
> This mail was sent to address EricHildum@earthlink.net
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Received on Wed Nov 9 08:54:12 2005