Methods for Phone GPS Tracking and Cell Phone Location raise the question: Do you really know where they are?
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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 moving. The newest smartphones have GPS locator functionality to track phone location. These features, along with others such as SMS texting, internet access and the capability to utilize other software make mobiles great gadgets. However GPS satellites aren’t always available, for example when the handset is in a building such as an school, mall, or even in an automobile. That doesn’t mean mobile phone locating 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 applications installed on the smartphone along 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 information and to make location mobile phone tracking faster.
Mobile phone GPS is what people usually think of when looking at locating mobile phones. GPS (Global Positioning System) using satellites is the most well known and more accurate means of tracking. But GPS needs satellites to be in direct line of site of the smartphone.
Sometimes heavy cloud cover and thick foliage interferes with signals.
If the phone is in a building, for example your house, mall. Some cell phones will keep 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 the frequency of taking GPS position. Selecting real-time or periodic sampling affects both the accuracy of determining position as well as how long the battery will last.
GPS receivers, whether in a smartphone, 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 health and estimated orbits of all GPS satellites (the almanac). GPS receivers sometimes 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 delay is sometimes caused if the GPS smartphone has been turned off for days or weeks, or has been transported 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 satellite signals and find initial position faster.
GPS Hot Start is when the GPS enabled handset recalls its last calculated position, the satellites that were in view at the time, the almanac data in memory, and attempts to find the same satellites and compute a new position based upon the previous data. This is almost always 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 known location, and almanac used, but not which satellites were in range. 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 kept 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 longer than other methods 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 cell phones connected to the cell network. It downloads the ephemeris and helps triangulate the smartphone general position. GPS Receivers can get a faster lock in exchange for a few kilobytes of data transmission.
A-GPS improves location tracking performance of cell phones (and other connected devices) in two ways:
The first way is by assisting to obtain a more rapid “time to first fix” (TTFF). AGPS acquires and storesinformation about satellite positionusing the cell network so the position information does require to be downloaded from the the satellite.
The next method is by helping locate cell phones 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 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 viable substitute to GPS mobile phone tracking. The position of the handset can be computed by the cell network cell id, that identifies the cell tower the phone is connected to. By knowing the location of this tower, then you can know approximately where the device is. But, 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 using CellID still provides a very useful alternative.
Another method of calculating device location 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 handset 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 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 variables. With Mobile Location Services (MLS), the GSM cellular network provider uses triangulation algorithms to calculate the position of the cell phone, its accuracy is proven to be less than than that of GPS. MLS is further affected by factors similar to GPS in the sense of the interference affecting signal quality and the density of GSM towers to help in the triangulation calculation. In remote areas position accuracy may be off as much as a mile.
In general 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. 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 via 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.
Keep in mind that there is a basic difference between smartphone GPS Tracking and Navigation. GPS phone tracking is normally related to someone maintaining records of either real-time or historical handset location, while Navigation deals with the smartphone user figuring out how to get from point A to point B.
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