Different Approaches to Being a Mobile Phone GPS Tracker Raise the Question: Do you really know where they are?

Mobile communications means more than just placing a phone call while on the move.    The latest mobiles have GPS locator functionality to track phone location.   These features, and others such as SMS texting, web access and the capability to utilize other applications make mobile phones great gadgets.  But GPS satellites aren’t always available, such as when the phone is in a structure such as an office, mall, or even in an automobile.  That doesn’t mean cell phone locating isn’t available, but it does mean there are other methods of being a locator.

To track a cell phone involves several main methods of determining  mobile phone position.  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 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 cellular provider.  Hybrid systems combine methods to make best use of available information and to make location phone tracking faster.  

Mobile phone GPS is what people usually think of when looking at tracking mobile phones.   GPS (Global Positioning System) using satellites is the most popular and more accurate technology of tracking.   However GPS needs satellites to be in direct line of site of the mobile phone. 

Sometimes thick cloud cover and thick foliage interferes with reception. 

If riding in a car the signals might not reach the smartphone.  Some cell phones will store the last known GPS location, others might not.  

Another issue with handset GPS location is the possibility of draining the battery.  It is important to be able to remotely adjust how often of taking GPS position.  Selecting real-time or periodic sampling affects both the accuracy of finding location along with battery life.  

GPS receivers, whether in a handset, or a dedicated GPS tracking device, determine position 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 longer to become ready to use 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 device  has been unused for days or weeks, or has been transported a far 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 signals and compute initial position more quickly. 

GPS Hot Start is when the GPS enabled device  remembers its last known position, the satellites that were in range at the time, the almanac information in memory, and tries 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 turned off. 

GPS Warm Start is when the GPS enabled handset  remembers its last calculated location, and almanac used, but not which satellites were in view. It resets and attempts  to connect to satellite signals and calculates a new position. 

The GPS receiver has a general idea of which satellites toseek because it stored its last known position and the almanac data helps identify which satellites are in range. 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 achieve a GPS lock. This takes the longest 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 telco operators developed Assisted GPS technology.   It downloads the ephemeris and helps triangulate the device   general position.  GPS Receivers can get a faster lock in exchange for a few kilobytes of data transmission.

A-GPS improves location tracking functions of cell phones (and other connected devices) in two ways:

One method is by helping to obtain a faster “time to first fix” (TTFF). Assisted GPS acquires and storesdata about satellite positionvia the cell network so the position information doesn’t need to be downloaded via the satellite. 

The second method is by helping position  devices when GPS signals are weak or not available.  As discussed above GPS satellite signals may be interfered with 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 useful alternative to GPS cell phone tracking.  The location of the smartphone can be estimated by the cellular network cell id, that identifies the cell tower the phone is using.   By knowing the position of this tower, then you can know approximately where the mobile phone  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 precision is less than than GPS accuracy. Nonetheless tracking from CellID still presents a very good alternative.    

Another way of calculating  cell phone 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, cell phone companies must be able to provide authorities with device 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 obtain accuracy down to 3-10m.  This depends upon many factors, as GPS signals are often very weak and are affected  by many variables.   With Mobile Location Services (MLS), the GSM cell network provider uses triangulation algorithms to estimate the position of the cell phone, its accuracy is proven to be less than than that of GPS.  MLS is further affected by the same issues as  GPS in the sense of the barriers affecting signal quality and the density of GSM towers to help in the triangulation calculation.   In rural areas location accuracy may be off as much as a mile. 

Generally speaking it comes down to 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 over the Internet.  How often GPS samples are taken and how often and by what method the information is sent to the server impact usefulness and costs. 

Consider that there is a basic difference between smartphone GPS Tracking and Navigation.  GPS mobile phone tracking is usually related to someone keeping records of either real-time or historical handset  position, 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 device 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    Cell Phone Monitoring Software  compatible with BlackBerry  and  Android  Smartphones, used or Parental Monitoring and Small Business Employee Monitoring .  

Visit this link for more information regarding the latest software for
Mobile GPS .

This entry was posted on Sunday, May 16th, 2010 at 1:03 am and is filed under Laptop Insurance Info. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.