Methods for Phone GPS Tracking and Cell Phone Location raise the question: Do you really know where they are?
Cell tracking, cell phone GPS and mobile phone track software are attracting attention from consumers, mobile phone companies and program developers. Mobile communications means more than just placing a phone call while on the move. The most recent smartphones have GPS locator functionality to track phone location. These features, along with others such as text messaging, internet access and the capability to use other software make cell phones great gadgets. But GPS satellites aren’t always available, for example when the handset is in a building such as an house, mall, or even in a car. That doesn’t mean smartphone 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 calculating smartphone position. GPS Global Positioning System-Satellites, Triangulation, and CellID. All these technologies convert smartphones into mobile tracking systems. These systems can be viewed as Network Based, Handset Based or a Hybrid approach. GPS location is Handset based as it requires software programs installed on the cell phone in conjunction 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 information and to make position phone tracking faster.
GPS on cell phones is what people usually think of when considering locating mobile phones. GPS (Global Positioning System) using satellites is the most popular and more accurate method of tracking. However GPS needs satellites to be in direct line of site of the cell phone. It doesn’t work particularly well indoors or in dense cities. If the phone is in a building, for example your house, mall, or often riding in a car the signals might not reach the smartphone. Sometimes thick cloud cover and dense trees interferes with signals. Some cell phones will retain the last known GPS location, others might not.
Another thing with handset GPS tracking is the potential of wasting 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 determining position along with battery life.
GPS receivers, whether in a mobile phone, or a dedicated GPS tracking device, calculate position by precisely timing the signals sent by GPS satellites. This information 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 longer to become ready to use after being turned on because it must acquire some basic information in addition to finding GPS satellite signals. This slow start is sometimes caused if the GPS mobile phone 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 capture satellite signals and find initial location more quickly.
GPS Hot Start is when the GPS enabled handset keeps its last known position, the satellites that were in view at the time, the almanac information in memory, and makes an attempt to obtain 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 switched off.
GPS Warm Start is when the GPS enabled smartphone recalls its last known location, and almanac used, but not which satellites were in view. It performs a reset and makes an attempt to obtain satellite signals and calculates a new position.
The GPS receiver has a general idea of which satellites tolook for because it stored its last known position and the almanac data helps identify which satellites are within view. 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 handset receiver has to attempt to lock onto a satellite signal from any available satellites.
In order to have better GPS lock times cellular manufacturers and wireless operators developed Assisted GPS technology. It downloads the ephemeris and helps triangulate the mobile phone general position. GPS Receivers can get a faster lock in exchange for a few kilobytes of data transmission.
Assisted GPS, also known as A-GPS or AGPS, improves the performance of standard GPS in devices connected to the cellular network. In the US Sprint, Nextel, Verizon Wireless, and Alltel all use A-GPS. Which is a means of using the cellular network to accelerate acquisition of GPS satellites. A-GPS assists location tracking functions of smartphones (and other connected devices) in a couple of ways:
One way is by assisting to obtain a faster “time to first fix” (TTFF). AGPS acquires and storesinformation about satellite locationvia the cellular network so the coordinates information doesn’t need to be downloaded from the the satellite.
The second way is by assisting locate handsets when GPS signals are weak or blocked. As mentioned before GPS satellite signals may be impeded by tall buildings, and do not penetrate building interiors well. A-GPS uses 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 substitute to GPS mobile phone tracking. The location of the cell phone can be calculated by the cellular 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 cell 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 precision is lower than GPS accuracy. Nonetheless tracking via CellID still provides a very viable substitute.
Another method of determining mobile phone 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 estimate position.
To comply with Federal Communications Commission guidelines, cellular 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 achieve accuracy down to 3-10m. 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 techniques to estimate the location of the device, its accuracy is proven to be less than than that of GPS. MLS is also impacted by the same issues as GPS in the sense of the interference affecting signal strength and the density of GSM towers to assist in the triangulation calculation. In remote 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. It may be important to consider how GPS location software applications handle the data and controls smartphone settings. Having real time tracking on demand, or preferring to minimize battery use and data transmission should be expected. Generally the application determines the location with a GPS receiver and transmits the tracking data to a server through a cellular packet 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 affect effectiveness and costs.
Consider that there is a basic difference between mobile phone GPS Tracking and Navigation. GPS cell phone tracking is typically related to someone keeping records of either real-time or historical mobile phone location, while Navigation deals with the handset user figuring out how to get from point A to point B.
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