How GPS Vehicle Tracking Works

When someone first considers vehicle tracking, the questions are usually the same: what exactly gets installed in the vehicle, how does the data reach me, and how reliable is it. The answer is not complicated, but it is made of several parts that work together. Here we follow the full path of a single data point, from satellite to screen, along with what turns out to matter in practice: what happens in a tunnel, how accurate the location is, and what the device measures besides position.

How the device knows where the vehicle is

GPS is a network of satellites orbiting the Earth and continuously broadcasting a signal that carries the exact time and their own position. The receiver in the vehicle only listens to that signal, it sends nothing back to the satellites. From the differences in how long the signal takes to arrive from several satellites it calculates its distance to each of them, and from those distances its own position. For a reliable position in three dimensions it needs at least four satellites: three for position and a fourth to correct its clock, since the clock in the receiver is nowhere near as precise as the atomic clocks on the satellites.

The name GPS itself refers to the American system, but today's devices simultaneously use the European Galileo, Russian GLONASS and Chinese BeiDou as well. The collective term for all of them is GNSS. The more satellites the receiver can see, the more accurate the position and the faster it locks on after the ignition is turned on, which is why multi-system support is now standard rather than an extra.

From the same signal the device also derives speed, heading and the exact time. That is why the speed reading from GPS tracking does not depend on the vehicle's own instruments, and why every record is time-aligned to the second, regardless of how many vehicles you track.

How the data reaches you

A position the device calculates is worth nothing until it reaches you. That is the job of the SIM card in the device, the same technology as in a phone, only intended for machines. The device connects to the server over the mobile network and sends it packets of data: position, speed, heading, ignition status and everything else that is connected to it.

How often it sends depends on the settings. While the vehicle is moving, every few seconds or on every change of direction is typical, so the route on the map follows the actual road instead of joining points with straight lines. While the vehicle is parked, the device reports less often. Events such as the engine starting, stopping or a sudden change in speed are sent immediately, without waiting for the next interval.

The amount of data is small. One vehicle uses a few megabytes a month, less than a short video clip, so a SIM with a data plan is normally part of the monthly subscription rather than a separate cost.

Abroad

For international transport it matters that the SIM works in roaming. In another country the device registers on the local network and keeps sending data the same way, so you track the vehicle in Germany or Turkey just as you do at home, with no extra equipment or setup. Before signing, it is worth checking whether roaming is included in the price and for which countries, because that is where offers differ. Our standard packages cover Serbia, the EU countries, the United Kingdom, the Scandinavian countries and Russia. We covered this and other questions to ask a provider in How to choose a GPS vehicle tracking system.

What happens without a signal

The mobile network is not everywhere. In a tunnel, on a stretch of road without coverage or inside a hall, the device cannot send data, but it does not stop recording it. It stores the data in its own memory and sends it as soon as the connection returns, with the original timestamp of every record. The route on the map fills in afterwards and nothing is lost. The same applies to the GPS signal: when the vehicle enters an underground garage, the device remembers the last known position and picks up the moment it sees satellites again.

What the device measures besides location

Location is the beginning, not the end. For a company, the value of the system usually comes from the data the device gets from the vehicle itself and from additional sensors.

• Ignition and engine. Whether the vehicle is running, how long the engine idles and how long stops lasted. Idling is one of the first costs that becomes visible once you start measuring.
• Driving style. A built-in accelerometer logs harsh braking, acceleration and sharp cornering. That is the basis for driver scoring and for eco-driving.
• Fuel. A probe in the tank measures the fuel level and logs every refuel and every sudden drop, which is the basis for consumption control and theft detection. More about the devices themselves on the fuel level sensors page.
• Data from the vehicle's computer. Over the CAN bus the device reads actual consumption, engine RPM, dashboard mileage, engine temperature and fault codes. On trucks and buses this goes through the FMS connector. Details on the telemetry and CAN bus page.
• Temperature. Sensors in the cargo area for the cold chain, with an alarm when the temperature leaves the set range. See temperature sensors.
• Who is driving. The driver logs in before the trip with an RFID card or iButton key, so the system knows who drove which vehicle and when. That is driver login.
• Heavy machinery. Engine hours instead of kilometers, and attachment operation. For trailers and machines without a permanent power supply there are devices with their own battery. See heavy machinery tracking.

An overview of every sensor that can be connected is on the Sensors page.

The platform: what happens to the data on the server

The server receives data from every vehicle and stores it. From the raw records the platform builds what you actually look at: live vehicle position, movement history for any day in the past, kilometers driven, driving and stopping time, visits to locations. All of it is available in reports, on demand or automatically by email, per vehicle, per driver or for the whole fleet.

The platform's other job is alarms. Instead of someone watching the map, the system reports on its own when something you defined in advance happens: the vehicle left a set zone, the speed limit was exceeded, the engine was started outside working hours, the fuel level dropped sharply, the device was disconnected from power. The notification arrives as an in-app message, email or SMS. This is also what vehicle anti-theft protection is built on.

Access is through a web app on a computer and a mobile app on a phone, with the same data. There is a separate app for drivers where they see their tasks and routes, and when needed a customer can be sent a temporary tracking link for a single delivery.

Installation: where the device sits and how long it takes

The device is about the size of a matchbox or a little larger. It is wired to the vehicle's power supply and to the ignition signal, and mounted in a hidden spot, usually behind the dashboard, so it is visible neither to the driver nor to anyone who might want to remove it. On trucks and buses it is additionally connected to the FMS connector to read data from the vehicle, while fuel and temperature sensors are installed separately.

Installation requires no work on the engine and does not change the vehicle's factory systems, and it normally takes between half an hour and an hour per vehicle, longer if fuel probes are installed as well. It is done at your location, so the vehicles do not have to go to a workshop. The device also has a small backup battery: if someone cuts the power, it keeps sending data for a while and immediately reports that the supply was interrupted.

Limitations worth knowing in advance

GPS tracking is reliable, but it is not magic, and it is better to know the limitations before rather than after.

• No sky, no signal. In a garage, tunnel or hall the device keeps the last position. Some devices then use the position of mobile network base stations, but that is a rough estimate, within hundreds of meters.
• Cities reduce accuracy. Tall buildings reflect the signal, so the location can be off by ten meters or so. For tracking a vehicle that rarely matters, and for calculating kilometers driven the platform applies corrections.
• Jammers exist. They are illegal in most countries, and serious systems detect jamming and report it as an alarm, the same as a power cut.
• The data is only as good as the installation. A badly connected or uncalibrated fuel probe gives bad data. That is why installation and calibration should be done by someone who does it every day.

What you need for the system to work

Less than people usually think. One device with a SIM card for each vehicle, and for you access to the platform, with no server or software you have to maintain yourself. Internet in the vehicle is not needed, the device has its own. All you need is a browser or a phone.

With us the system can be tried free for 15 days on your own vehicles, with the device installed and full access, so you decide based on your own data. What the monthly subscription includes and what it costs per vehicle is on the GPS vehicle tracking pricing page, and an overview of the whole system on the Tracking page.

Frequently asked questions