subject: How to use A-GPS technology to track cell phone numbers [print this page] How to use A-GPS technology to track cell phone numbers
All cell phones continually broadcast radio signals even when they're not being used. Cellular phone companies have been able to approximate the location of mobiles for years using triangulation information from towers that receive the signals. But with the introduction of cell phone GPS technology, the information obtained has become more accurate.
GPS receivers, whether in a cell phone, or a dedicated GPS tracking device, calculate position by precisely timing the signals sent by GPS satellites. This data 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 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 can be caused when the GPS cell phone has been unused for days or weeks, or has been transported a far distance while turned off for.
If satellite signals are not available, or accuracy is less important than battery life, using Cell-ID is a good substitute to GPS cell phone tracker. The location of the smartphone can be computed by the cellular 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 cell phone is. However, a tower can cover a huge area, from a few hundred meters, in high population areas, to several miles in lower density areas. This is why location CellID precision is lower than GPS accuracy. Nonetheless location from CellID still provides a very useful alternative.
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 determine initial position more quickly.
In order to have better GPS lock times cellular manufacturers and network 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.
