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Methods for Cell Phone Tracking and Cell Location raise the question: Do you really know where they are?

By: PhoneBeagle


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To track a mobile phone involves several main methods of calculating mobile phone location. GPS (Global Positioning System/Satellites), Triangulation, and CellID. All these technologies convert smartphones into mobile tracking devices. These systems can be viewed as Network Based, Handset Based or a Hybrid approach. GPS location is Handset based as it needs software programs installed on the cell phone in conjunction with GPS hardware. Triangulation and CellID are Network Based as they use the equipment and information from the cellular provider. Hybrid systems combine techniques to make best use of available data and to make position cell phone tracking faster.
Mobile phone GPS is what people commonly think of when considering locating smartphones. GPS (Global Positioning System) using satellites is the most common and more accurate means of tracking. However GPS requires satellites to be in direct line of site of the mobile phone. It doesn't work particularly well indoors or in dense cities. If the handset is in a building, for example your office, restaurant, or often sitting in an automobile the signals might not reach the mobile phone. Sometimes heavy cloud cover and dense trees impedes with signals. Some mobile phones will retain the last known GPS location, others might not.
Another thing with mobile phone GPS tracking is the possibility of battery drain. It is important to be able to remotely adjust how often of taking GPS position. Choosing real-time or periodic sampling affects both the resolution of determining position along with battery life.
GPS receivers, whether in a cell phone, or a dedicated GPS tracking device, calculate location by precisely timing the signals sent by GPS satellites. This information includes the time the message was transmitted, precise orbital information (the ephemeris), and the general system health and estimated orbits of all GPS satellites (the almanac). GPS receivers sometimes take longer to become ready to navigate after it's turned on because it must acquire some basic information in addition to finding GPS satellite signals. This slow start is sometimes caused when the GPS device has been turned off for days or weeks, or has been moved a significant distance while unused for. The GPS must update its almanac and ephemeris data and store it in memory. The GPS almanac is a set of data that every GPS satellite transmits. When a GPS receiver has current almanac data in memory, it can acquire satellite signals and find initial position more quickly.
GPS Hot Start is when the GPS enabled smartphone keeps its last calculated location, the satellites that were in view before, the almanac information in memory, and makes an attempt to find the same satellites and compute a new position based upon the previous data. This is usually the quickest GPS lock but Hot Start only works if the phone is in the same general area as when the GPS was last turned off.
GPS Warm Start is when the GPS enabled mobile phone recalls its last calculated position, and almanac used, but not which satellites were in view. It performs a reset and makes an attempt to find satellite signals and calculates a new position.
The GPS receiver narrows the choice of which satellites tolook for because it stored its last known position and the almanac data helps identify which satellites are visible in the sky. The Warm Start will take longer than the Hot Start but not as long as a Cold Start.
With GPS Cold Start, the device dumps all the previous data, and attempts to locate satellites and accomplish a GPS lock. This takes more time because there is no known reference information. The GPS enabled cell phone receiver has to try to lock onto a satellite signal from any available satellites.
In order to have better GPS lock times mobile phone manufacturers and network operators introduced Assisted GPS technology. It downloads the ephemeris and helps triangulate the smartphone general position. GPS Receivers can get a faster lock at the expense of a few kilobytes of data transmission.
Assisted GPS, also known as A-GPS or AGPS, improves the performance of standard GPS in handsets connected to the cellular network. In the United States Sprint, Nextel, Verizon Wireless, and Alltel all use Assisted GPS. Which is a means of utilizing the cellular network to accelerate finding of GPS satellites. A-GPS assists location tracking performance of cell phones (and other connected devices) in a couple of ways:
The first method is by assisting to obtain a faster "time to first fix" (TTFF). A-GPS acquires and storesinformation about satellite positionusing the cellular network so the position information does require to be downloaded from the the satellite.
Another way is by helping locate devices when GPS signals are weak or blocked. As mentioned before GPS satellite signals may be impeded by tall buildings, and do not penetrate building interiors well. AGPS utilizes proximity to cellular towers to estimate location when GPS signals are not available.
If satellite signals are not available, or accuracy is less important than battery life, using Cell-ID is a useful substitute to GPS mobile phone tracking. The position of the handset can be calculated by the cellular network cell id, that identifies the cell tower the phone is using. By knowing the location of this tower, then you can know approximately where the smartphone is. But, a tower can cover a huge area, from a few hundred meters, in high populationdensity areas, to several miles in lower density areas. This is why location CellID precision is less than than GPS accuracy. Nevertheless location using CellID still presents a very viable substitute.
Another method of calculating device position is Triangulation or Mobile Location Services (MLS). Cell Tower Triangulation uses signal analysis data to calculate the time it takes signals to travel from your phone to at least three cell towers to estimate location.
To comply with Federal Communications Commission guidelines, cellular phone companies must be able to provide authorities with cell phone latitude and longitude to an accuracy of 50 to 300 meters. Cell Tower Triangulation doesn't always meet this requirement. For comparison, commercially available GPS systems are able to achieve accuracy down to less than 10 meters. This depends upon many factors, as GPS signals are often very weak and are affected by many environmental factors. With Mobile Location Services (MLS), the GSM cellular network provider utilizes triangulation techniques to compute the location of the smartphone, its accuracy is proven to be less than than that of GPS. MLS is also affected by the same issues as GPS in the sense of the barriers impeding signal strength and the density of GSM towers to help in the triangulation effort. In rural areas position accuracy may be off as much as a mile.
Generally speaking it comes down to what location tracking system is available, and the requirements for accuracy. Hybrid methods are emerging that use various techniques in tandem to provide best available location given available resources. It might be important to consider how GPS location software applications handle the data and controls smartphone settings. Having real time tracking on demand, or preferring to minimize battery use and data transmission should be expected. Generally the application determines the location with a GPS receiver and transmits the tracking data to a server through a cellular packet data connection. The data connection to the server is usually made over the Internet. How often GPS samples are taken and how often and by what method the information is sent to the server affect effectiveness and costs.
Consider that there is a basic difference between mobile phone GPS Tracking and Navigation. GPS mobile phone tracking is usually associated with a third-party maintaining records of either real-time or historical smartphone location, while Navigation deals with the cell phone user determining how to get from point A to point B.

Article Source: http://depositarticles.com/

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