The global positioning system is comprised of three distinct segments: space, ground stations and user.
Space holds the satellites that transmit the signals as they orbit above the Earth in a predictable path. Ground stations monitor these signals, performing updates as necessary to keep optimal precision and ensuring the health of the global navigation system. The user segment is comprised of all the GPS tracking devices located on the planet.
The satellites orbit the Earth in a predictable path. This means their exact location is always known, even though they are moving. Because their location is known, they become reference points in the sky.
When GPS trackers receive the signals from the satellites, the messages include the time the messages were sent. The GPS tracking devices compare the time the messages were sent to the time they were received. Based on this difference, they can determine their location in relation to the satellite.
The messages travel at the speed of light. Satellites are equipped with incredibly precise atomic clocks. To make GPS tracking devices affordable, instead of having atomic clocks, they rely on 4 satellites to determine an accurate location.
While 3 satellites can determine the location of GPS tracking devices, 4 are used because there will be one out of the group that doesn't intersect with the others. The GPS tracker detects this inconsistency and subtracts the difference to determine the accurate location.
There are two main types of GPS trackers: those that store data within the unit and those that transmit it to a central location using cellular, radio or satellite modem that is embedded in the unit. The central location database can also be an internet-connected computer.
The location data of the GPS tracking devices are laid over a map. More advanced systems use real-time maps to see the current movements of an asset.
A GPS tracker that is a data logger keeps record of an asset's location at regular intervals. It stores this data in its internal memory, whether that is a memory card slot or an internal flash memory with a USB port. Some GPS tracking devices work like a USB flash drive, enabling downloading of the location data, which can then be further analyzed on a computer.
Data pushers are GPS tracking devices that send the location data to a dedicated server. This server will store and analyze data instantly, which the user can access typically with web-based software.