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Methods for Cell Phone Tracking and Mobile Location Raise the Question:  Do you really know where they are?

Mobile communications means more than just making a phone call while on the move.    The hottest smartphones have GPS locator features to track phone location.   These features, and others such as text messaging, web access and the capability to use other applications make mobile phones great gadgets.  However GPS satellites aren’t always available, for example when the handset is in a structure such as an school, mall, or even in a car.  That doesn’t mean cell phone tracking isn’t possible, but it does mean there are other methods of being a tracker.

To track a cell phone involves several main methods of determining  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 requires software applications installed on the smartphone  in conjunction with GPS hardware.  Triangulation and CellID are Network Based as they use the equipment and data from the wireless provider.  Hybrid systems combine methods to make best use of available information and to make location mobile phone tracking faster.  

Mobile phone GPS is what people usually think of when looking at tracking smartphones.   GPS (Global Positioning System) using satellites is the most common and more accurate technology of tracking.   But GPS requires satellites to be in direct line of site of the cell phone. 

Sometimes thick cloud cover and thick foliage interferes with signals. 

If the phone is in a building, for example your house, mall.  Some smartphones will keep the last known GPS location, others might not.  

Another thing with mobile phone GPS location is the potential of wasting the battery.  It is important to be able to remotely adjust the frequency of taking GPS position.  Selecting real-time or periodic sampling affects both the resolution of determining location as well as battery life.  

GPS receivers, whether in a cell phone, or a dedicated GPS tracking device, determine position by precisely timing the signals sent by GPS satellites.  This data includes the time the message was transmitted, precise orbital information (the ephemeris), and the general system condition and estimated orbits of all GPS satellites (the almanac).  GPS receivers often take a long time to become ready to use 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 capture signals and calculate initial location faster. 

GPS Hot Start is when the GPS enabled smartphone  remembers its last calculated location, the satellites that were in range before, the almanac data in memory, and attempts to lock onto the same satellites and compute a new position based upon the previous information. This is generally the quickest GPS lock but Hot Start only works if the phone is generally in the same location as when the GPS was last turned off. 

GPS Warm Start is when the GPS enabled device  remembers its last known position, and almanac used, but not which satellites were in view. It resets and tries  to lock onto satellite signals and computes 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 deletes all the previous information, and attempts to locate satellites and achieve a GPS lock. This takes more time because there is no known reference information.  The GPS enabled mobile phone   receiver has to try to lock onto a satellite signal from any available satellites. 

Assisted GPS, also known as A-GPS or AGPS, improves the performance of standard GPS in mobile phones 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 cell network to speed up finding of GPS satellites.  GPS Receivers can get a faster lock in exchange for a few kilobytes of data transmission.

A-GPS assists location tracking performance of smartphones (and other connected devices) in a couple of ways:

The first method is by helping to obtain a faster “time to first fix” (TTFF). Assisted GPS acquires and archivesinformation about the location of satellitesusing the cellular network so the position information does need to be downloaded via the satellite. 

The second way is by helping locate  cell phones when GPS signals are weak or not available.  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 calculate 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 good substitute to GPS smartphone location.  The location of the device can be determined by the cell network cell id, that identifies the cell tower the phone is connected to.   By knowing the position of this tower, then you can know approximately where the mobile phone  is.  But, a tower can cover a huge area, from a few hundred meters, in high density areas, to several kilometers in lower density areas. This is why location CellID accuracy is lower than GPS accuracy. Nevertheless tracking from CellID still presents a very viable alternative.    

Another method of determining  handset 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 determine location.   

To comply with Federal Communications Commission guidelines, cellular phone companies must be able to provide authorities with smartphone 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 impacted  by many environmental factors.   With Mobile Location Services (MLS), the GSM cellular network provider uses triangulation techniques to calculate the position of the handset, 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 interference impeding signal strength and the density of GSM towers to assist in the triangulation effort.   In rural areas location accuracy may be off as much as a mile. 

Generally speaking it is a matter of 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.   Typically the application determines the location with a GPS receiver and transmits the tracking data to a server through a data connection. The data connection to the server is usually made using the Internet.  How often GPS samples are taken and how often and by what method the data is sent to the server impact effectiveness and costs. 

Keep in mind that there is a basic difference between cell phone GPS Tracking and Navigation.  GPS cell tracking is usually related to someone keeping records of either real-time or historical cell phone  location, while Navigation deals with the smartphone  user determining how to get from point A to point B.

A really great software package that includes remote control of mobile phone settings, and combines Mobile Phone Tracking  with SMS text message, Call Log,  MMS multi-media message monitoring, and a web account for storage and review is PhoneBeagle.  

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Tags: cell phone track, employee monitoring, mobile phone GPS tracking, parental control

Saturday, March 27th, 2010 • General