GPS receivers use a network of satellites to determine their location with an accuracy measured in meters. In addition to being a valuable aid to navigation, GPS technology can power extremely accurate tracking devices. These monitors can help you keep track of valuables, monitor children or adults with special needs, or even call for help in the wilderness.
The GPS network consists of a series of satellites in precise orbits designed to provide every point on Earth maximum coverage. Each satellite broadcasts data about its current position, as well as the origin time of the broadcast. When a GPS receiver detects this signal, it calculates how long the signal took to reach the receiver, and from that data, determines how far away the receiver is from that point in space. Once a receiver detects at least four of these signals, it can calculate its position on the planet with significant accuracy.
While GPS satellite signals provide navigational information, that part of the GPS system is one-way. In order for a GPS receiver to serve as a tracking device, it needs some way to report that information. In urban environments, a cellular modem may be the best choice, since most cities and major thoroughfares have reasonable cell tower coverage. Outside of developed areas, a GPS tracker will need a satellite radio to provide uninterrupted tracking data to observers.
GPS trackers can work automatically, providing position updates to observers at regular intervals, or they may take advantage of geofencing. Geofencing sets a particular geographic area as the tracker’s safe zone, and if the tracker leaves that area, the device can initiate a call for help and begin tracking. This setup works well for GPS trackers attached to large valuables or for personal trackers for children and at-risk adults. A child’s school could be designated a safe zone, and if the tracker in his backpack leaves the school grounds at an unauthorized time, the device can sound an alarm.
Since GPS trackers rely on satellite signals for navigational information, these devices work best outdoors. The GPS satellite network provides enough coverage that even a partially obscured view of the sky may allow a position calculation, but if the target takes a GPS tracker indoors or underground, it may not be able to report its current location. In addition, GPS receivers may pick up radio echoes bouncing off large buildings or mountains, causing some uncertainty in the positional calculation until the system can find a more reliable set of signals.
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