GPS receivers often take longer to become ready to navigate after it's turned on because it must acquire some basic information in addition to finding GPS satellite signals. This delay is sometimes caused when the GPS device 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 acquire satellite signals and find initial location more quickly. |
To be able to get improved GPS lock times cellular manufacturers and system operators created Assisted GPS technology. This downloads the ephemeris helping triangulate the device general position. GPS Receivers can get a quicker lock in exchange for a few kilobytes of data transmission.
Assisted GPS, also called A-GPS or AGPS, increases the performance of normal GPS in handsets connected to the cellular network. In America Sprint, Nextel, Verizon Wireless, and Alltel all use AGPS. This is a means of utilizing the cell network to accelerate finding of GPS satellites. A-GPS improves location tracking performance of mobile phones (along with other related devices) in a couple of ways:
The first way will be assisting to secure a more rapid "time to first fix" (TTFF). A-GPS acquires and archives information regarding satellite location via the cell network and so the location data does not need to be downloaded from the the satellite.
A subsequent method is by assisting position devices when GPS signals are weak or not available. Because GPS satellite signals may be impeded by tall buildings, and do not penetrate building interiors well AGPS makes use of distance to cellular towers to estimate location when GPS signals are not available.
When satellite signals are not obtainable, or accuracy and precision is less important than life of the battery, employing Cell-ID is a viable alternative to GPS mobile phone tracking. The location of the mobile phone might be determined by the cell network cell id, which identifies the cell tower the mobile phone is using. By knowing the location of the tower, you may know roughly the place that the device is. Nonetheless, a tower can cover a massive area, from a few hundred meters, in high populationdensity areas, to several kilometers in lower density areas. This is the reason location CellID precision is lower than GPS accuracy. Having said that monitoring from CellID still delivers a truly handy substitute.
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