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

Across the country and around the world, GPS tracking, mobile GPS and cell phone GPS track software are attracting attention from consumers, mobile phone companies and program developers.   The newest mobile phones include GPS locator functionality to track phone location.   These features, along with others such as SMS texting, internet access and the ability to use other applications make mobiles great gadgets.  However GPS satellites aren’t always available, for example when the phone is in a structure such as an school, mall, or even in an automobile.  That doesn’t mean mobile phone tracking isn’t possible, but it does mean there are other ways of being a locator.

To track a mobile phone involves several main methods of formulating  cell phone location.  GPS Global Positioning System-Satellites, Triangulation, and CellID.   All these technologies convert cell phones 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 data from the wireless provider.  Hybrid systems combine methods to make best use of available data and to make location cell phone tracking faster.  

GPS on cell phones is what people commonly think of when looking at locating mobile phones.   GPS (Global Positioning System) using satellites is the most common and more accurate technology of tracking.   However GPS requires satellites to be in direct line of site of the handset. 

It doesn't work as well indoors or in dense cities. 

If sitting in an automobile the signals might not reach the smartphone.  Some smartphones will store the last known GPS location, others might not.  

Another thing with mobile phone GPS location is the possibility 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 finding position along with how long the battery will last.  

GPS receivers, whether in a smartphone, or a dedicated GPS tracking device, compute location by precisely timing the signals transmitted by GPS satellites.  This information includes the time the message was transmitted, precise orbital information (the ephemeris), and the general system condition and rough orbits of all GPS satellites (the almanac).  GPS receivers sometimes take a long time to become ready to navigate after being turned on because it must acquire some basic information in addition to capturing GPS satellite signals. This slow start is sometimes caused if the GPS device  has been turned off for days or weeks, or has been transported a significant distance while turned off 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 compute initial location more quickly. 

GPS Hot Start is when the GPS enabled smartphone  remembers its last known location, the satellites that were in view before, the almanac data in memory, and tries to connect to the same satellites and determine a new position based upon the previous information. This is usually 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 cell phone  remembers its last known position, and almanac used, but not which satellites were in range. It resets and makes an attempt  to connect to satellite signals and calculates a new position. 

The GPS receiver narrows the choice of which satellites toseek 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 more time than the Hot Start but not as long as a Cold Start. 

With GPS Cold Start, the device dumps all the previous information, and attempts to locate satellites and achieve a GPS lock. This takes longer than other methods because there is no known reference information.  The GPS enabled device   receiver has to attempt 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 devices connected to the cellular network.   In America  Sprint, Nextel, Verizon Wireless, and Alltel all use AGPS. This is a means of using the cellular network to accelerate 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:

One method is by assisting to obtain a more rapid "time to first fix" (TTFF). AGPS acquires and archivesinformation about satellite positionvia the cell network so the coordinates information doesn’t need to be downloaded via the satellite. 

The second way is by assisting position  smartphones when GPS signals are weak or blocked.  As discussed above GPS satellite signals may be interfered with by tall buildings, and do not penetrate building interiors well. Assisted GPS utilizes proximity to cellular towers to compute 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 alternative to GPS cell phone tracking.  The position of the device can be estimated 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 handset  is.  However, a tower can cover a huge area, from a few hundred meters, in high density areas, to several miles in lower density areas. This is why location CellID accuracy is lower than GPS accuracy. Nonetheless tracking from CellID still provides a very useful alternative.    

Another method of calculating  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 estimate position.   

To comply with Federal Communications Commission guidelines, cell 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 can 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 utilizes triangulation algorithms to compute the position of the mobile phone, 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 quality and the density of GSM towers to help in the triangulation effort.   In rural areas location accuracy may be off as much as a mile. 

In general it is a matter of what location tracking system is available, and the need 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 via the Internet.  How often GPS samples are taken and how often and by what method the data is sent to the server impact usefulness and costs. 

Keep in mind that there is a basic difference between cell phone GPS Tracking and Navigation.  GPS mobile phone tracking is usually associated with a third-party maintaining records of either real-time or historical mobile phone  position, while Navigation deals with the cell phone  user figuring out how to get from point A to point B.

A really great software package that includes remote control of cell phone settings, and combines Phone GPS 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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