A GPS tracking unit is a device, normally carried by a moving vehicle or person, that uses the Global Positioning System to determine and track its precise location, and hence that of its carrier, at intervals. The recorded location data can be stored within the tracking unit, or it may be transmitted to a central location database, or Internet-connected computer, using a cellular (GPRS or SMS), radio, or satellite modem embedded in the unit. This allows the asset's location to be displayed against a map backdrop either in real time or when analyzing the track later, using GPS tracking software. Data tracking software is available for smart phones with GPS capability.
GPS tracking unit architecture
A GPS tracker essentially contains a GPS module to receive the GPS signal and calculate the coordinates. For data loggers it contains large memory to store the coordinates, data pushers additionally contains the GSM/GPRS modem to transmit this information to a central computer either via SMS or via GPRS in form of IP packets.
Types of GPS trackers
Usually, a GPS tracker will fall into one of these three categories, though most Graphemically phones can work in any of these modes according to mobile applications installed:
Typical GPS logger
A GPS logger simply logs the position of the device at regular intervals in its internal memory. Modern GPS loggers have either a memory card slot, or internal flash memory card and a USB port. Some act as a USB flash drive. This allows downloading of the track log data for further analysis in a computer. The track list or point of interest list may be in GPX, KML, NMEA or other format.
Most digital cameras save the time a photo was taken. Provided the camera clock was reasonably accurate or used GPS as its time source, this time can be correlated with GPS log data, to provide an accurate location. This can be added to the Exit metadata in the picture file. Cameras with GPS receiver built in can directly produce such a geotagged photograph.
In some private investigation cases, data loggers are used to keep track of a target vehicle. The PI need not follow the target so closely, and always has a backup source of data.
Data pusher is the most common type of GPS tracking unit, used for asset tracking, personal tracking and Vehicle tracking system.
Also known as a GPS beacon, this kind of device pushes (i.e. "sends") the position of the device as well as other information like speed or altitude at regular intervals, to a determined server, that can store and instantly analyze the data.
A GPS navigation device and a mobile phone sit side-by-side in the same box, powered by the same battery. At regular intervals, the phone sends a text message via SMS or GPRS, containing the data from the GPS receiver. Newer GPS-integrated smart phones running GPS tracking software can turn the phone into a data pusher (or logger) device; as of 2009 open source and proprietary applications are available for common Java ME enabled phones, iPhone, Android, Windows Mobile, and Symbian.
Most 21st-century GPS trackers provide data "push" technology, enabling sophisticated GPS tracking in business environments, specifically organizations that employ a mobile workforce, such as a commercial fleet. Typical GPS tracking systems used in commercial fleet management have two core parts: location hardware (or tracking device) and tracking software. This combination is often referred to as an Automatic Vehicle Location system. The tracking device is most often hardwire installed in the vehicle; connected to the CAN-bus, Ignition system switch, battery. It allows collection of extra data, which later gets transferred to the GPS tracking server, where it is available for viewing, in most cases via a website accessed over the internet, where fleet activity can be viewed live or historically using digital maps and reports.
GPS tracking systems used in commercial fleets are often configured to transmit location and telemetry input data at a set update rate or when an event (door open/close, auxiliary equipment on/off, geofence border cross) triggers the unit to transmit data. Live GPS Tracking used in commercial fleets, generally refers to systems which update regularly at 1 minute, 2 minute or 5 minute intervals, whilst the ignition status is on. Some tracking systems combine timed updates with heading change triggered updates.
GPS tracking solutions are recently being used in mainstream commercial auto insurance these are sometimes called Telematics 2.0.
The applications of trackers of this kind include:
Law enforcement. An arrested suspect out on bail may have to wear a GPS tracker, usually an ankle monitor, as a bail condition. GPS tracking may also be ordered for persons subject to a restraining order. Race control. In some sports, such as gliding, participants are required to carry a tracker. In particular this allows race officials to know if the participants are cheating, taking unexpected shortcuts, and how far apart they are. This use was illustrated in the movie Rat Race. Espionage/surveillance. A tracker on a person or vehicle allows movements to be tracked. This application is used by private investigators. These devices are also used by some parents to track their children. Some devices can send text alerts to the parents for every unexpected place visited by the child. GPS personal tracking devices are used in the care of the elderly and vulnerable. Devices allow users to call for assistance and optionally allow designated carers to locate the user's position, typically within 5 to 10 metres. Their use helps promote independent living and social inclusion for the elderly. Devices often incorporate either 1-way or 2-way voice communication. Some devices also allow the user to call several phone numbers using pre-programmed speed dial buttons. Trials using GPS personal tracking devices are also underway in several countries for use with early stage dementia. Some Internet Web 2.0 pioneers have created their own personal web pages that show their position constantly, and in real time, on a map within their website. These usually use data push from a GPS enabled cell phone or a personal GPS tracker. Sports: the movements of a rambler, cyclist, etc., can be tracked. Statistics such as instantaneous and average speed, and distance traveled, are logged. Adventure sports: GPS tracking devices such as the SPOT Satellite Messenger are available that allow the position of a person to be tracked. In particular this allows rescue personnel to locate the carrier. These devices allow the carrier to send messages, even when out of cellular telephone range. Monitoring employees. GPS-handled tracking devices with built-in cellphone are used to monitor employees by various companies, specially those engaged in field work.
Solar Powered. The advantage of some solar powered units is that they have much more power over their lifetime than battery powered units. This gives them the advantage to report their position and status much more often than battery units which need to conserve their energy to extend their life. Some wireless solar powered units, such as the RailRider can report more than 20,000 times per year and work indefinitely on solar power eliminating the need to change batteries.
Animal control. When put on a wildlife animal (e.g. in a collar), it allows scientists to study its activities and migration patterns. Vaginal implant transmitters mark the location where pregnant females give birth. Animal tracking collars may also be put on domestic animals, to locate them in case they get lost.
Aircraft can be tracked either by ADS-B (primarily airliners), or by FLARM data packets picked up by a network of ground stations (primarily used by General Aviation aircraft, gliders and UAVs), both of which are data pushers. ADS-B is to be superseded by ADS-C, a data puller.
GPS data pullers are also known as GPS transponders. Unlike data pushers that send the position of the devices at regular intervals (push technology), these devices are always on, and can be queried as often as required (pull technology). This technology is not in widespread use, but an example of this kind of device is a computer connected to the Internet and running gpsd.
These can often be used in the case where the location of the tracker will only need to be known occasionally e.g. placed in property that may be stolen, or that does not have constant source of energy to send data on a regular basis, like freights or containers.
Data Pullers are coming into more common usage in the form of devices containing a GPS receiver and a cell phone which, when sent a special SMS message reply to the message with their location.
Covert GPS Trackers
Covert GPS trackers contain the same electronics as regular GPS trackers but are constructed in such a way as to appear to be an everyday object. One use for covert GPS trackers is for power tool protection, these devices can be concealed within power tool boxes and traced if theft occurs.