A GPS tracking unit is a device that uses the Global Positioning System to determine the precise location of a vehicle, person, or other asset to which it is attached and to record the position of the asset at regular intervals. The recorded location data can be stored within the tracking unit, or it may be transmitted to a central location data base, 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 GPS tracking unit Architecture
Typical GPS tracker architecture
A GPS tracker essentially contains 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. The diagram depicts a hardware architecture of an advanced GPS tracker. Types of GPS trackers
Usually, a GPS tracker will fall into one of these three categories, though most smartphones, being GPS Phones, can work in all these modes, depending on which mobile applications are installed: [Data loggers
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 and a USB port. Some act as a USB flash drive. This allows downloading of the track log data for further analyzing in a computer. The tracklist 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 the GPS was used as a 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, thus geotagging it. In some Private Investigation cases, these data loggers are used to keep track of the vehicle or the fleet vehicle. The reason for using this device is so that a PI will not have to follow the target so closely and always has a backup source of data. 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. Most of the modern 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 fleets 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 get 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...