There are two ways that celluar (cell) phones are located, depending on the
cell phone itself, and the technology that is built in to that cell phone.
Older cell phones are located via a process of signal triangulation, while
newer phones have a Global Postitioning System (GPS) built in to them. In
practice, one, the other or both can be used to locate a cell phone.
Triangulation can be done on most any cell phone, depending on the location
of the cell phone and any nearby towers. GPS locating depends on the cell
phone being so equipped. There is a federal mandate that pretty much all
cell phone companies, including Verizon, will be able to locate a cell phone
based on one, the other or both methods.
Here is more information on both processes.
IT Digest - Ingenious Tejas's Digest Blog
"Cell phones are two way radio transmitters that work by connecting to a
nearby tower and exchanging data. Despite the FCC's limitation on maximum
power output of a cell phone, they are still able to connect with towers
miles away at UHF frequencies ... Because cell phones put out a constant RF
output (sometimes pulsed) they can be tracked using the tower triangulation
method where the network administrators can find your precise location with
their administrative network access."
The Graduate School and University Center at the City University of New York
(CUNY) has "Intro to Mapping Sciences" taught by Doug Williamson.
"Phase II of the FCC regulations will begin to be implemented in the fall of
2001. During Phase II, wireless carriers and the PSAPs will be upgrading
their systems to provide more exact geographic coordinates. Two methods will
1) triangulation: new receivers will be added to the tower arrays that will
be able to perform triangulation; and 2) global positioning receivers (GPS)
may be added to new wireless phones."
"Cell-phone companies add tracking abilities" was a Knight Ridder distributed
article, dated Wednesday, July 20, 2005, written for the Dallas Morning News
by Terry Maxon, here presented on the Portsmouth Herald web site.
"However, a federal mandate requiring cell phones to automatically tell 911
centers where the caller is located has speeded adoption.
That can be accomplished through ground-based triangulation, in which the
phone's location is determined by figuring its relative distance from various
cell stations. But most large cellular companies appear to be embracing the
Nextel has had GPS technology in every phone since November 2002. Sprint and
Verizon phones also contain GPS technology, allowing them to provide locator
services if they desire."
This last article is a great one to read, as it speaks to how the technology
has commerical applications, such as allowing shuttle companies track their
vans and giving directions to people over their cell phones.
Here are some Verizon links on the subject and related services they offer.
Frequently Asked Questions - Answers to FAQs
"The GPS (Global Positioning System) locator chip, which is present in all
wireless phones we currently sell, except the BlackBerry 6750, is used solely
for tracking purposes by Emergency 911 Services and does not function like a
typical GPS device.
Phase II Enhanced 911 rules requires wireless carriers to automatically
provide the telephone number of the 911 caller and far more precise location
information, within 50 to 100 meters in most cases.
The first two steps have been implemented, however the third step (Phase II)
is still in progress."
Small/Medium Business - Fleet Administrator
"Locate, monitor and manage vehicles equipped with the necessary vehicle
tracking hardware from any office computer."
The technical terms for these services are ones such as "cellular phone GPS
locating" and "cellular phone signal traingulation" and E991 locating.
The requirements for this technology came from the Federal Communications
Commission (FCC) wireless "Enhanced 911" (E911) rules.
"The wireless E911 program is divided into two parts - Phase I and Phase II.
Phase I requires carriers, upon appropriate request by a local Public Safety
Answering Point (PSAP), to report the telephone number of a wireless 911
caller and the location of the antenna that received the call. Phase II
requires wireless carriers to provide far more precise location information,
within 50 to 300 meters in most cases."
More information on Phase II from this Wireless Advisor forum.
"In the second phase, cell phone companies have two options for significantly
improving the locating capacity. They can install GPS chips in their
telephones. The chip determines the phone?s location (in hours, minutes, and
seconds of longitude and latitude) by receiving signals beamed down from an
array of satellites. The chip determines the location based on different
arrival times of these signals. Alternatively, a cell phone company can
comply with the mandate by using information provided by its network. This
approach uses towers and antennae in the carrier's network to measure the
timing of signals emitted from the phone, and thus its location ..."
If you need any clarification, please feel free to ask.
Google search on: "cellular phone" tracking OR tracing triangulation
Searched the Verizon Wireless site for: GPS
Looking Forward, denco-ga - Google Answers Researcher