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How to Use GPS with a Cell Phone
Newer and more powerful cell phones (smart phones) provide a convenient and affordable way to access the GPS system for using mobile location-based services. But there are some limitations. The GPS cell phone options and services described will help you decide on a cell phone that meets your GPS needs.
• Overview of GPS
Overview of GPS
The Global Positioning System (GPS) is a system of 24 space-based satellites that provides physical location (position) and time information anywhere on the Earth. It is owned and operated by the United States government. It is a free service available to anyone with a GPS receiver device. The GPS is used to provide positioning, navigation, and timing services.
Most cell phones made after 2001 have some type of GPS capability that can be used for location, navigation, and tracking activities.
With a GPS-capable cell phone, you can see a real-time map and find your location. You can type an address, see it on a map, and get turn-by-turn directions to get there. You can track the movement of a person (with a GPS device) or a vehicle. A cell phone with GPS works like a handheld or automotive GPS device, with a few differences.
A phone that does not have GPS capability built-in can determine its location using its signal and the cellular network. The minimum location-based activity that all cell phones can do is transmit their location to an emergency call center after dialing 911. But newer smart phones can do more with GPS.
Development of Cell Phones and GPS
In 2001, the U.S. Federal Communications Commission mandated wireless Enhanced 911 Phase 2 that when a cell phone dials 911 the wireless service provider must provide to an emergency call center (Public Safety Answering Point) the caller's telephone number, the location of the cellular network site or base station transmitting the call, and the latitude and longitude of the caller's phone accurate to 50 to 300 meters. Compliance was waived until 2005. Accuracy was deferred until September 2012.
The Canadian Radio-television and Telecommunications Commission in Canada required wireless service providers to upgrade their 911 services by February 2010.
The location of the cell phone is determined by a GPS chip in the handset that uses a system called Assisted GPS (A-GPS). The A-GPS chip is cheaper, uses less power, works faster, and provides location data in places where a conventional GPS receiver with a full GPS chip might have difficulties working (due lower signal strength and location accuracy) such as inside buildings, near tall buildings or trees, or in tunnels.
A-GPS works by sending satellite signal information to a computer on the cellular network which has network reference data and processes the incoming data faster than the processing by a GPS receiver, so data is transmitted quicker and results are more accurate than what a receiver can provide on its own. A-GPS chips lock onto the first satellite faster (lower Time to First Fix to acquire a satellite signal, determine navigation data, and calculate a position), needs only two GPS satellites (versus three or more for conventional GPS receiver), and are accurate to 5 to 50 meters (versus 3 to 15 meters). The network computer acts as an offline GPS receiver and sends the location back to your phone and to the PSAP.
The A-GPS chip is usually turned off in a phone by the wireless provider unless 911 is dialed or you pay for location services because it uses up some cellular bandwidth and consumes battery power. For phones without a full GPS chip, you cannot use the GPS if you do not have cell phone service.
Newer handset designs, such as some smartphones, include a full GPS chip. Location functionality is a combination of GPS processing and cellular network location processing (triangulate the location of nearby cell transmitters) depending on signal strengths. If the cell network is used, data charges depend on your calling plan with the wireless provider. Using the phone in autonomous (standalone) GPS mode does not use the cellular network or incur cellular data charges. But it will consume more battery power and might incur GPS service fees.
A recent technology for use in cell phones called Simultaneous GPS (S-GPS) uses both the GPS and cellular network simultaneously, so it can perform faster than traditional A-GPS.
Phones without Assisted GPS (A-GPS) chips need an additional handheld GPS receiver that mounts on the vehicle's dashboard. The phone connects to it through a wire or a Bluetooth wireless connection.
Phones with full GPS chips are complete GPS receivers and do not need any additional GPS hardware. For a 911 call, some cellular network resources are also used for faster location data processing.
To receive GPS signals, the GPS device should have an unobstructed view of the sky so the satellites are clearly visible. The GPS signals are not affected by weather and will go through clouds, plastic, and glass (except metal-coated, wire-mesh, and bulletproof glass). But GPS signals do not work indoors because buildings, concrete, rock/stone, metal, and heavy foliage will block GPS signals. In an automobile, it is best to place the GPS receiver on or near the dashboard so that it can receive GPS signals through the glass windshield.
GPS has struggled to serve users in cities and other environments with
obstructions. In downtown areas, the satellite signals are blocked, weakened
How to Access Location-based Services
A location-based service (LBS) uses a wireless network, such as the cellular network or GPS, to determine the geographical position of a wireless device such as a cell phone or GPS receiver. The data is used to provide information related to the location and movement of the mobile device, the location and movement of another device, or the location of a known place.
Some popular uses for location-based services are:
There are four basic ways of accessing mobile location-based services:
1. Wireless Service Provider
The wireless service provider provides a navigation service for compatible cell phones within its network coverage area. The cost of navigation services varies, but is about $10 a month or $3 a day (data included).
Some national services available in the U.S. and Canada are:
2. Third-party Internet-based Service Provider
The cell phone usually must have a program installed on it to use the service. The software has features such as offline map storage, topographic data for off-road navigation, or address data. You must pay fees for a cell phone data plan (preferably unlimited). Prices for the LBS provider range from free to $60 or a subscription fee.
Some third-party Internet-based service providers are:
3. Dedicated GPS Device
One-time purchase of a handheld or vehicle-mounted GPS receiver. No subscription fees. Typical purchase prices range from $60-700 for handheld devices and $700-2,000 for vehicle (in-dash) systems depending on features. Map updates can be free or paid. Works without a cell phone.
The top 3 providers of dedicated handheld GPS receivers are Garmin, TomTom and Magellan. There are many other makers of GPS devices for general use or specific LBS applications.
4. Automotive Telematics Systems
An embedded GPS system installed by the vehicle manufacturer. Access emergency help, road-side assistance, or navigation services from a vehicle. Available from carmakers such as Ford Sync (requires Bluetooth-enabled phone), General Motors OnStar, Honda/Acura Navigation System, Toyota Navigation System Lexus Safety Connect, and Mercedes-Benz mbrace. Prices range from free to $400 a year plus map updates. Works without a cell phone.
How to Enable A-GPS Services on Your Cell Phone
Some wireless providers allow customers that have handsets with A-GPS chips to turn on the GPS functionality full-time. It's up to the carrier to enable standalone A-GPS mode. Although depending on the handset you might be able to find a hack to turn it on yourself.
To use the A-GPS feature, cell phone users must subscribe to their cellular
providers GPS-services bundle (see above).
Bluetooth GPS and Cell Phones
You don't have to use A-GPS with monthly data fees to use GPS with a cell phone. You can use a Bluetooth phone to connect with a Bluetooth GPS receiver.
The Bluetooth receiver transmits GPS data to the phone while navigation software on the phone displays your location and other information on a moving map.
Use the Bluetooth GPS receiver (speakerphone) for safer hands-free calling.
Compare Cell Phones with Dedicated GPS Devices
The cell phone is basically a portable phone, with navigation features added on as best can be done in a small device. It does not have the size and power of a dedicated GPS receiver for location-based activities such as navigation. But cell phones are rapidly getting more powerful and some have larger displays.
GPS-enabled cell phones and dedicated handheld GPS receivers differ in the following ways:
Portability - A cell phone can be used as a handheld GPS device for out-of-car purposes. A vehicle dash-mounted GPS device cannot. An outdoor GPS receiver is designed for outdoor use, but is inconvenient for in-vehicle use and navigation.
Ruggedness - Outdoor GPS receivers are rugged and waterproof for outdoor use in bad weather and with backpacks. Cell phones are fragile and can get scratched.
Screen size - The screen size of most GPS-enabled cell phones is too small (2 to 4 inches diagonal) and has too low resolution for easy touch-screen control and accurate navigation display such as scrolling around the map. GPS receivers have larger displays (3.5 to 7 inches diagonal) and touch-controls specifically designed for navigation.
Position accuracy - Non-GPS phones and A-GPS phones are not as accurate as handheld or automotive GPS receivers. Full GPS cell phones are as accurate, but lack the processing power to run the navigation application fast, so there might be a delay in operation.
Cell phone reception - A-GPS phones depend on cellular service for navigation. In places where cell service is unavailable or weak, such as tower distance, hilly terrain or tall buildings, no location-based service would be available.
GPS reception - Buildings, large trees, concrete, and stone will block or weaken GPS signals causing GPS service to be spotty or unavailable. In downtown, you might miss a turn and get lost. Cell phones usually receive a strong and stable signal in most downtown areas.
Feature upgrades - New and improved navigation applications are constantly being made available for cell phones, which you can download. The functionality of a dedicated GPS receiver can not be upgraded.
Costs - Cell phones used for LBSs have monthly fees compared to dedicated GPS receivers, which have a one-time purchase (sometimes plus updates).
Battery life - Using a cell phone with LBSs can quickly discharge the handset battery (as little as one hour of use), in addition to phone use. Dedicated GPS devices run on 12-volt power in the vehicle. Some GPS receivers use standard AA or AAA batteries, which are portable, can last 12 hours, and can be recharged.
Can a Cell Phone Replace a Dedicated GPS Receiver?
Can a cell phone with GPS functionality replace a dedicated GPS receiver? For some limited location-based features and functionality, yes. But for regular, detailed, or specialized location-based activities, no. A dedicated GPS receiver is more accurate, reliable and dependable for navigation than a cell phone.
If you want to use a cell phone for frequent or detailed navigation use, get a handset with a large display and a high battery capacity.
If you travel far, often, along complicated routes, or to unknown destinations, it will be worthwhile to get a dedicated GPS receiver that has more features and is the most you can afford.
Summary of Using GPS with a Cell Phone
The technology and operation of using GPS with a cell phone are varied and changing. What GPS system works for you depends on your application, skills, comfort, and budget.
Handsets with no GPS functionality get basic location data for 911 using triangulation of cellular network transmitters. It is fast but usually has low accuracy. Some location-based service applications are available (based on radio tower ID) but they have low accuracy.
Handsets with A-GPS chips use a combination of GPS resources and cellular network resources to calculate position with fair-to-good accuracy. A cellular network signal, with data plan charges, is required for location-based functionality. An A-GPS chip that is turned on consumes more handset battery power. The A-GPS chip might not be able to lock on to weak GPS signals.
Handsets with full GPS chips provide functionality comparable to conventional GPS receivers. A cellular network signal (and charges) is not needed for GPS. The handset is able to lock on to weak GPS signals. Using the GPS feature consumes more battery power.
The small screens of most cell phones are awkward to use for frequent or detailed navigation activities.
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