Wikipedia
An IVMS (In Vehicle Monitoring System) combines the installation of an electronic device in a vehicle, or fleet of vehicles, with purpose-designed computer software at least at one operational base to enable the owner or a third party to track the vehicle's location, collecting data in the process from the field and deliver it to the base of operation. Modern vehicle tracking systems commonly use GPS technology for locating the vehicle, but other types of automatic vehicle location technology can also be used. Vehicle information can be viewed on electronic maps via the Internet or specialized software.
Urban public transit authorities, Mining companies and Transport/Freight companies are an increasingly common user of vehicle tracking systems.
Several types of vehicle tracking devices exist. Typically they are classified as "passive" and "active".
"Passive" devices store GPS location, speed, heading and sometimes a trigger event such as key on/off, door open/closed. Once the vehicle returns to a predetermined point, the device is removed and the data downloaded to a computer for evaluation. Passive systems include auto download type that transfer data via wireless download. one such example of a passive device would be a GPS Log Book that gathers the data and stores it for later upload
"Active" devices also collect the same information but usually transmit the data in real-time via cellular or satellite networks to a computer or data center for evaluation. The information is typically analysed and presented using web based technologies.
Many modern IVMS devices combine both active and passive tracking abilities: when a cellular network is available and a tracking device is connected it transmits data to a server; when a network is not available the device stores data in internal memory and will transmit stored data to the server later when the network becomes available again.
Historically IVMS has been accomplished by installing a box into the vehicle, either self-powered with a battery or wired into the vehicle's power system. For detailed vehicle locating and tracking this is still the predominant method; however, many companies are increasingly interested in the emerging cell phone technologies that provide tracking of multiple entities, such as both a salesperson and their vehicle. These systems also offer tracking of calls, texts, Web use and generally provide a wider safety net for the staff member and the vehicle.
IVMS Units track many different types of activity within a vehicle such as GPS Position, Various inputs such as seatbelt and 4x4 engagement, Speed, Impact/Rollover, Harsh events (acceleration and deceleration, usually performed by a Triaxial Accelerometer) over revving, excess idle time just to mention a few.