Cell Phone GPS – How does it work?


How does cell phone GPS work?

In times past if you wanted to know your exact location or get navigation assistance you needed a dedicated GPS device, like a Garmin or a TomTom. These days most cell phones have GPS receivers built-in, particularly those manufactured since February 2005.

In 2005, the FCC required that, for the purpose of locating cell phone callers in an emergency, when a cell phone user rang 911 it should automatically transmit information on the caller’s location to the PSAP (Public Safety Answering Point). Cell phone manufacturers responded to the new requirements (known as E911) by building phones with GPS receivers built-in that could provide location information, pinpointing a caller’s position to within 6 meters.

GPS or GPRS – What’s the difference?

Many people feel that GPS and GPRS are similar or work together. Possibly this is simply because they sound the same.

Actually the only thing they have in common is that they both use radio waves to transmit information. Aside from that they serve two completely different purposes.

GPS stands for Global Positioning System and is a network of satellites that transmit radio waves, providing location information to people on the ground.

GPRS stands for General Packet Radio Services and is a system that transmits data using radio waves and cell towers between GPRS devices like cell phones and GPRS modems.

Read one of our previous blog posts for more information on how GPS works.

When a caller dials 911, the GPS-enabled cell phone sends the latitude and longitude information it has received from the GPS network to their cell phone company using their cell phone network. The cell phone company releases that information to the PSAP receiving the call, so they can pinpoint the caller’s location. This is particularly useful if the person is unable to communicate their address or doesn’t know where they are.

Can I use my GPS cell phone to get turn-by-turn directions?

Just because your cell phone has GPS it doesn’t mean that it can necessarily be used as a navigation device. As an aside your cell phone may also have GPRS; don’t confuse this with GPS as the two systems are quite different (see the box ‘GPS or GPRS – What’s the difference?’).

For your cell phone to use the information received from GPS satellites it needs software that can understand the information it receives from a GPS satellite.

GeoBase is an example of a software application (or geospatial mapping engine) that can translate GPS satellite data, converting latitude and longitude information into a point on a map. Many software makers, such as Telogis, develop fleet management software programs using GeoBase to convert information from GPS satellites into usable navigation information.

More and more phones, such as the iPhone or the Sony Ericsson Satio, are coming out with GPS-enabled applications that provide turn-by-turn navigation, linking directly to sites such as Google Maps. In addition to getting directions, there are many other location-based applications that can provide you with information on nearby points of interest or communicate your current location to another person, such as an employer or parent.

Does a cell phone with GPS invade my privacy?

With it now being compulsory for all cell phone manufacturers to build phones with a built-in GPS receiver some have voiced concerns about this information being misused for government departments to track civilians. Are these concerns warranted?

The FCC addressed privacy issues when it introduced the new requirements by explicitly requiring that cell phone GPS only be used for E911 emergency calls only. For any other situations, consent would be needed from the cell phone owner or a court order obtained.

Cell phone GPS tracking has been denied by the courts in several cases presented by law enforcement agencies wanting to track suspects. If there is no actual evidence of criminal activity, then courts have not permitted cell phone companies to release any GPS tracking information.

What do you think of the FCC requiring all cell phones to have GPS tracking enabled? Is it too much like ‘big brother’? Do you think it’s abused by government agencies?

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One Response to “Cell Phone GPS – How does it work?”

  1. william Says:

    Im fine with GPS tracking. I dont do anything I shouldnt and its just as easy to leave the cell phone at home if one didnt want the wife to know he’d been to the porn store :-D.
    Its a great feature. I got lost a couple weeks ago and didnt know i had GPS on my phone. Looking at it the other day I realized I could have used it to get me exactly where I was trying to get to.
    Very helpful feature.

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