A GPS vehicle tracker is conceptually simple: a small box, hidden somewhere in the car, that knows where it is and tells someone. The implementation, though, involves three or four distinct technologies working in sequence — and understanding what each one does explains a lot about why trackers behave the way they do.
The device itself
A typical UK self-install tracker is a box roughly the size of a deck of cards. Inside it are four key components:
- A GNSS receiver — picks up signals from positioning satellites
- A cellular modem — sends data back to base via a mobile network
- A small backup battery — keeps it running if the vehicle power is cut
- A microcontroller — the "brain" that decides when to report and when to alert
That's the whole device. Everything else — relay attack resistance, geofencing, journey logging — is either a software feature of the microcontroller or a feature of the cloud service the device reports to.
Step 1: Knowing where it is
GNSS stands for Global Navigation Satellite System. It's the umbrella term for the four main satellite positioning constellations:
- GPS — the US-operated system, 31 satellites
- GLONASS — Russian, 24 satellites
- Galileo — European, 28 satellites
- BeiDou — Chinese, 35 satellites
Modern trackers receive signals from at least two of these (typically GPS + GLONASS in UK consumer kit). Each satellite continuously broadcasts its position and the precise time. The tracker calculates its own position by measuring how long the signals take to arrive from at least four satellites simultaneously.
The result is a latitude/longitude position accurate to within about 5 metres in open sky conditions. Inside a multi-storey car park, under heavy tree cover, or in a dense urban canyon, accuracy degrades to 15-20 metres — and sometimes the device temporarily can't get a fix at all.
"Real-time" tracking is a slight misnomer. Most devices report position every 30 seconds to every few minutes — the exact interval is a trade-off between battery life, cellular data costs, and how live you need the data to be. When an alert fires, the rate jumps to per-second updates.
Step 2: Telling someone
Once the device knows where it is, it sends that data back to a cloud service using the cellular network. This is where a lot of the differences between trackers come from.
The cellular link uses a SIM card embedded in the device. UK consumer trackers almost always use a "multi-network roaming SIM" — one that can connect to EE, O2, Vodafone or Three depending on which has the best signal at the moment. This is crucial for rural coverage: a single-network SIM might be deaf in parts of Cumbria or the Highlands where one network has weak coverage but another is fine.
The cellular packets are encrypted (TLS over the cellular link is standard) and small — typically a few hundred bytes per report. A device reporting every minute consumes around 50-100MB of data per year.
Step 3: When the cellular link fails
Two scenarios commonly take the cellular link offline: dense urban environments where signal is genuinely weak, and intentional jamming attacks where thieves use a small device to block GSM frequencies around the vehicle.
Modern trackers handle this in two ways. First, they buffer position data locally and burst-upload as soon as signal returns. So a 10-minute drive through a tunnel results in a 10-minute gap visible in real-time tracking, but the journey log fills in correctly once the device reconnects.
Second, they use inertial dead-reckoning — onboard accelerometers and gyroscopes that estimate position based on motion, even when no satellites or cellular are available. This is how a tracker can still tell you "the vehicle moved 1km west" even during a signal blackout. The accuracy degrades over time (each minute of dead-reckoning adds error), but it's usually enough to bridge short outages.
Step 4: Power
The device draws its power from the vehicle's permanent 12V supply — typically via a fuse-tap into a circuit that's always live (not one that switches off with the ignition). Standby current is around 25mA, which is roughly the same as the vehicle's clock and stereo memory combined. A healthy battery can sit unused for weeks without significant drain.
The internal backup battery kicks in if main power is cut — for example, if a thief disconnects the device or removes the vehicle battery. Typical backup capacity is 48-72 hours of cellular reporting before the unit goes dark. That's usually more than enough time for a recovery operation to complete.
Step 5: The "smart" layer
The microcontroller is what decides when to bother humans. It's running firmware that:
- Checks every 30 seconds whether the vehicle is inside its registered geofence
- Watches for ignition events (vehicle starting outside expected use windows)
- Monitors for tamper events (case opened, power cut, fuse pulled)
- Detects collision via accelerometer thresholds
- Holds the journey log and the recent position buffer
This layer is where most of the meaningful differences between products live. Cheap trackers basically just report position; better ones do intelligent filtering — they don't bother you with normal driving but do reliably catch genuine threats.
What to ignore in tracker marketing
Several common marketing claims are essentially noise:
- "Military-grade encryption" — TLS over cellular is industry standard. Nobody has anything more exotic.
- "99.9% accuracy" — GPS doesn't have a percentage figure; it has a metres figure. Any "99%" claim is using the wrong unit.
- "Quantum positioning" — this doesn't mean anything as a consumer feature.
- "Live satellite tracking" — all GPS tracking is live by definition; the question is the reporting interval to the cloud, not the GPS fix itself.
The things that do differ between products: SIM quality (roaming or single-network), backup battery life, dead-reckoning sophistication, alert-rule intelligence, monitoring centre capability, and the recovery service around the hardware.
The bottom line
GPS tracking is well-understood, mature technology. The device part of the equation is roughly comparable across the market — most reputable products use similar chips, similar SIMs, similar firmware patterns. What differs dramatically, and what actually matters when your vehicle is stolen, is everything that happens after the device fires an alert. Buy the alerting, monitoring and recovery service, not the device.