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

Posted on 02 April 2010

Across the country and around the world, GPS tracking, cell phone GPS and cell phone tracking software are getting a lot of attention from consumers, mobile phone companies and program developers.   The latest smartphones include GPS position functionality to track phone location.   These features, and others such as SMS texting, web access and the capability to use other applications make mobiles great gadgets.  But GPS satellites aren’t always available, for example when the handset is in a structure such as an office, mall, or even in a car.  That doesn’t mean smartphone 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 formulating  smartphone position.  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  along with GPS hardware.  Triangulation and CellID are Network Based as they use the equipment and information from the wireless provider.  Hybrid systems combine techniques to make best use of available data and to make location cell tracking faster.  

Mobile phone GPS is what people usually think of when considering tracking smartphones.   GPS (Global Positioning System) using satellites is the most well known and more accurate method of tracking.   But GPS needs satellites to be in direct line of site of the smartphone. 

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

If the phone is in a structure, for example your school, restaurant.  Some mobile phones will keep the last known GPS location, others might not.  

Another issue with smartphone 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 finding position as well as battery life.  

GPS receivers, whether in a mobile phone, or a dedicated GPS tracking device, determine location by precisely timing the signals transmitted by GPS satellites.  This data 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 delay can be caused if the GPS cell phone  has been turned off for days or weeks, or has been moved a far 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 compute initial position more quickly. 

GPS Hot Start is when the GPS enabled handset  recalls its last known position, the satellites that were in range at the time, the almanac information in memory, and makes an attempt to connect to the same satellites and compute 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 switched off. 

GPS Warm Start is when the GPS enabled device  keeps its last calculated location, and almanac used, but not which satellites were in view. 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 tolook for because it kept 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 data, 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 smartphone   receiver has to attempt to lock onto a satellite signal from any available satellites. 

In order to have better GPS lock times mobile phone manufacturers and telco operators developed Assisted GPS technology.   It downloads the ephemeris and helps triangulate the device   general position.  GPS Receivers can get a faster lock at the expense of a few kilobytes of data transmission.

A-GPS improves location tracking functions of mobile phones (and other connected devices) in a couple of ways:

The first way is by assisting to obtain a more rapid “time to first fix” (TTFF). Assisted GPS acquires and storesdata about the location of satellitesusing the cell network so the coordinates information does need to be downloaded via the satellite. 

The second way is by assisting position  cell phones when GPS signals are weak or impeded.  As discussed above GPS satellite signals may be interfered with by tall buildings, and do not penetrate building interiors well. A-GPS utilizes proximity to cellular towers to calculate position 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 cell phone location.  The location of the cell phone can be estimated by the cell network cell id, which identifies the cell tower the phone is using.   By knowing the location of this tower, then you can know approximately where the device  is.  However, a tower can cover a huge area, from a few hundred meters, in high population areas, to several kilometers in lower density areas. This is why location CellID precision is lower than GPS accuracy. Nonetheless tracking using CellID still presents a very good alternative.    

Another way of calculating  smartphone 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 cell phone latitude and longitude to an accuracy of 50 to 300 meters.   Cell Tower Triangulation doesn’t always meet this requirement.  By way of comparison commercially available GPS systems can obtain 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 uses triangulation algorithms to calculate the position of the device, its accuracy is proven to be much worse than that of GPS.  MLS is also impacted by factors similar to  GPS in the sense of the interference affecting signal strength and the density of GSM towers to help in the triangulation effort.   In remote areas location accuracy may be off as much as a mile. 

It might be critical to consider how GPS location software applications handle the data and controls cell phone settings.   Having real time tracking on demand, or preferring to minimize battery use and data transmission should be offered.   Generally 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 over 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. 

Consider that there is a basic difference between handset GPS Tracking and Navigation.  GPS phone tracking is typically associated with a third-party keeping records of either real-time or historical handset  location, while Navigation deals with the handset  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 Cell Phone Tracking  with SMS text message, Call Log,  MMS multi-media message monitoring, and a web account for storage and review is PhoneBeagle.  

Follow this link if you are interested in    Mobile Monitoring Software  compatible with BlackBerry  and  Android  Smartphones, used or Parental Monitoring and Small Business Employee Monitoring .  

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GPS Tracking .