<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=ISO-8859-1">
<title></title>
</head>
<body text="#000000" bgcolor="#ffffff">
Date: Fri, 24 Feb 2006 14:56:54 +0000<br>
<pre wrap="">From: Steve Kennedy <a class="moz-txt-link-rfc2396E"
href="mailto:steve-asterisk@gbnet.net"><steve-asterisk@gbnet.net></a>
Subject: Re: [Asterisk-Users] GPS-enabled cell phone/PDA
On Fri, Feb 24, 2006 at 07:17:52AM -0600, Rich Adamson wrote:
</pre>
<blockquote type="cite">
<pre wrap=""><span class="moz-txt-citetags">> </span>Its my understanding the cell phone coordinates are sent to the cell phone
<span class="moz-txt-citetags">> </span>provider and their equipment reads (and holds) that data. Its not part
<span class="moz-txt-citetags">> </span>of any data available to you in any form unless you talk to the cell
<span class="moz-txt-citetags">> </span>provider and convience them you have a valid need. Highly unlikely in
<span class="moz-txt-citetags">> </span>the US anyway. Even if you could convience them to provide it, they
<span class="moz-txt-citetags">> </span>would likely demaand some sort of out-of-band data transmission facility.
</pre>
</blockquote>
<pre wrap=""><!---->
GSM networks have the Cell ID available to the phone, however that's not
much use without the location of the cellsite.
There are now location based services, whereby you can query the network
and they'll give out an approximate location (most cells are sectored
[6 sectors per cell) which gives a direction, the cell also knows what
power the phone is transmitting with, and the power it's received so can
make a good approximation of where the phone is (within 60 degrees
angle). However it's likely a phone will be picked up by several cells,
so the network can triangulate and make a better aproximation.
Making the information available to end-users is problematic due to
privacy issues, unless the user explicitly agrees to give the info away.
With GPS units, the info is stored in the phone and can send it out
using SMS or other means.
</pre>
-------------<br>
It was my impression that only a handful of cellphones have full GPS
units in them. Benefon and some Motorola units made for the former
Nextel come to mind. The Benefon units do send SMS reports, and in
fact, I have written code to control and track these units via SMS
using a Nokia 31 GSM terminal. Unfortunately, aside from their unique
GPS/SMS capability, the Benefons are not very attractive products, in
my opinion. And they are expensive. The Motorola units contain Java
machines and a well defined API for accessing the location data. I
have not worked with them. There have undoubtedly been changes in the
marketplace since I did this work about 2 years ago.<br>
<br>
As I understand it (but don't have thorough knowledge and could be
mistaken), other units generally only receive GPS satellite signals and
relay the data to cellular provider networks where the actual location
calculation is done. This can be done with assistance of data obtained
based on tower proximity, which jumpstarts the iterative process of
approximation. I think it is called assisted GPS or some such...<br>
</body>
</html>