On Fri, 04 Apr 2008 21:12:28 -0400, "Richard B. Gilbert"
<rgilbert88@comcast.net> wrote:

>Roger 2008 wrote:
>> "Gordon Burditt" <gordonb.sh6xy@burditt.org> wrote in message
>> news:XrOdnYKg7an-52vanZ2dnUVZ_vOlnZ2d@internetamerica...
>>
>>>>Please do not forget who the original poster was and his questions: He
>>>>asked:
>>>>"can I display my own LAT/LON values somehow without a map application ?"
>>>
>>>For some cell phone implementation of "GPS" (this one doesn't involve
>>>actual satellites talking to your phone), your position coordinates
>>>are present at the cell towers and somewhere in the offices of Big
>>>Brother, but not on your cell phone. If a map application can get
>>>your position at all, it has to ask your cell provider to send it,
>>>and that may cost money.
>>
>>
>> Oh yeah, now that you mention it. My first camera phone called it GPS but
>> when you read further about it, it was just using cell phone towers.
>>
>> BTW I have met a person with an iPHONE that thinks his phone has GPS and he
>> even showed me "Google Maps for Mobile" on it.
>>
>> I thought he had a messed up GPS reading because it had us way across the
>> street and then I learned later the iPHONE uses cell phone towers for an
>> approximate location on "Google Maps for Mobile."
>>
>>
>
>GPS, or at least the civilian version of it, is only accurate to within
>about 300 feet or 100 meters. I once did a "site survey" using a
>Motorola M12+T GPS timing receiver. The software I used plotted
>something like 10,000 position readings on the map. The result was a
>strip about 10 meters wide and 100 meters long and oriented ENE-SSW. My
>antenna was more or less in the middle of this mess.
>
>The military uses a different set of signals from the same satellite and
>gets accurracy good enough for weapons targeting. This level of GPS is
>available only to the military and certain defense contractors. Us
>lowly civilians can't get it.
>
>As far as I know, a cell phone tower has no means of determining the
>direction your signal is coming from.

Towers cannot tell what direction the signal is coming from, but can
tell from relative power how far away it is, and form a circle based
on that reading. For sake of argument, say you are 3 miles from
tower one, and 5 miles from tower two. there are only two places you
can be 3 milies and 5 miles from the towers. Add a third tower, and
you only have one place you can be. That is how triangulation (hence
the tri - three) works.