How to Find a Person by GPSby David Lipscomb
You probably use the Global Positioning System to find your place in the world, plotting locations on virtual maps and guiding you where you want to go. GPS is also used to find people equipped with GPS devices. Children, Alzheimer's patients and criminals can all be located with dedicated GPS trackers, or through location information emitted by a smartphone.
GPS Tracking Devices
GPS tracking devices are mounted in vehicles, typically in discrete locations to avoid detection. Used by private investigators and law enforcement, these units transmit in real time or can be retrieved to download movement data. Businesses frequently use these units to monitor fleet vehicles, enabling owners and managers to examine the amount of time the vehicles were in motion as well as their current locations.
GPS systems are usually pretty reliable, given the relatively weak signal beamed to satellites and back to Earth. One of the primary limitations of GPS, however, is the inability of satellites to track individuals when they're indoors. Indoor Positioning Systems -- IPS -- potentially solve this issue by relying on Wi-Fi, Bluetooth and near-field communications technologies to triangulate an individual's position. Smartphones that rely on cell towers already use a form of this in practical terms, because their positioning relies on accurate tower data. Other technologies use the last known GPS point, relying on a device's accelerometer and gyroscope to estimate your position. Vehicle GPS devices use a form of IPS, relying on gyroscopes as well as vehicle-speed sensors mounted near the axle. These measures allow fairly accurate positioning of the vehicle as it travels through a bridge or under heavy foliage.
Depending on the device and service, data can be directly uploaded to a computer via USB from the GPS device. This practice is fairly common with removable GPS tracking units. Other services allow devices to be located on virtual maps, after signing in with account information. For example, various cell phone location apps find your device and place it on a virtual map on your PC or other browser-enabled device. Specialized devices for tracking children and victims of dementia offer similar location features, including logs of previous locations.
GPS trackers have come under legal scrutiny, in some cases for allegedly violating illegal search-and-seizure laws when these devices are placed in vehicles. Government officials sought to be able to acquire GPS data from cell phone providers without warrants, citing the risk that the delay in getting warrants might cause. In 2012, the United States Supreme Court unanimously disagreed in its United States v. Jones ruling, citing the Fourth Amendment's reasonable expectation of privacy.
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