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 analysing the track later, using GPS tracking software. Data tracking software is available for smartphones with GPS capability.

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 TRACKER

  1. DATA LOGGERS:

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 allowsdownloading 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 Exif metadata in the picture file. Cameras with GPS receiver built in can directly produce such a geotagged photograph.

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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.

 

2.  DATA PUSHERS

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 smartphones 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.

 

SOURCE:    wikipedia