How to track a vehicle in a car park or a tunnel, where there are no satellites

The dispatcher looks at the map: the vehicle pulled up at a shopping centre and vanished. Forty minutes later it appears again, two blocks from the entrance. What happened in between is anybody's guess. For a delivery service that is a disputed delay, for a rental company a question about where the customer drove, and in a theft it is a lost trail.

Let us look at why this happens and what can be done about it.

Why the track breaks off underground

A tracker's satellite receiver is a radio receiver listening to a very weak signal. The satellites follow orbits about 20,000 km up, and by the time the signal reaches an antenna on a vehicle it is so weak that any obstacle kills it.

The reinforced concrete floor of a car park, the roof of a tunnel, a metal container: none of them is transparent to this signal. The receiver does not "lose accuracy", it simply stops seeing the satellites. The last point on the track is the place where the vehicle went under a roof.

Multi-constellation reception deserves a separate word. A tracker that sees GPS, GLONASS, Galileo and BeiDou at once works more reliably in dense building and in gorges, as we wrote in the article on GNSS and GPS. But under concrete no system helps: there are no satellites in sight at all.

Dead reckoning: how a tracker works out the path without satellites

The idea is an old one, used by sailors for centuries: if you know what speed and heading you held and how much time has passed, you can work out where you are without seeing the shore. In English it is called dead reckoning.

In a tracker the part of the compass and the log is played by two sensors:

• The accelerometer shows acceleration: pulling away, braking, bumps in the road.
• The gyroscope shows rotation: which way and by how much the vehicle has turned from its previous heading.

While the satellites are visible the coordinates come from them. As soon as the signal is lost, the tracker starts working the position out itself, starting from the last known point. When the vehicle comes out of the tunnel and the satellites return, the position is corrected from them and the accumulated error is cleared.

To the dispatcher it looks like one unbroken line. Inside the car park the line is drawn by calculation, outside by satellites, and the switch happens by itself.

Where it is genuinely needed

Underground car parks

In Baku this is the commonest case: the car parks of shopping centres, residential complexes and office buildings, and multi-storey car parks. For a rental or leasing company it matters to know that the vehicle is in that particular place rather than "somewhere in the area". In a theft the difference is sharper still: a track that reaches the entrance of one specific garage narrows the search to a single address.

Tunnels and underpasses

An ordinary tracker simply jumps over a short tunnel: two points, before and after, with a straight line between them. If the tunnel is long or has a fork, that straight line lies — the vehicle could have turned off. With dead reckoning you can see which way it actually went.

Covered warehouses and sheds

A forklift, or a vehicle that drives inside a warehouse to be loaded, disappears from the map. For recording loading time that matters: without a track there is no telling whether the vehicle was queueing or had left.

GPS jammers

A jammer is a small device that floods the satellite band with noise. The tracker sees that the signal is being suppressed and sends an alert, but it stops receiving coordinates. Dead reckoning carries on drawing the track from the motion sensors.

According to figures quoted by Teltonika, 64% of vehicle thefts in Mexico in 2024 involved signal jamming. That is a different country and a different market, but the tool is the same everywhere, and it does not cost much.

An honest word about the limits

Dead reckoning is a calculation, not a measurement, and that is worth saying plainly.

• The error builds up. Every minute without satellites adds some inaccuracy to the calculation. For driving into a car park or through a tunnel there is enough margin; for an hour of driving under a jammer there is not, although the direction of travel will still be clear.
• Mobile coverage is needed. The tracker works the path out, but it can only send the points over the mobile network. Underground there often is none: the data then builds up in the device's memory and arrives once the vehicle drives out. So you will see the track inside the car park, but not in real time.
• The tracker has to be fixed rigidly. If the device rattles about under the dashboard, the gyroscope will take the shaking of the case for a turn of the vehicle. That is why the mounting, and calibration on a drive after fitting, are a condition of the thing working rather than a formality.
• Firmware cannot add it. Dead reckoning runs on physical sensors inside the tracker. If there is no gyroscope in the device, a software update will not create one — a different model is needed.

Which hardware can do it

Teltonika makes a separate line for jobs like this, the FT platform. For typical scenarios the manufacturer recommends the FTC927: a compact LTE Cat 1 tracker with a built-in gyroscope and accelerometer, Bluetooth 5.4 for beacons and sensors, and an output for an immobiliser relay. According to the data sheet it tracks up to 41 visible satellites at once and receives GPS, GLONASS, Galileo and BeiDou.

If your vehicles never go underground and there are no tunnels on their routes, there is no point paying extra for a gyroscope: an ordinary compact tracker will do. The difference in price is small, but so is the sense in a feature that is never used.

A detailed look at the theft scenario is in the case study on recovering stolen vehicles.

What to allow for in Azerbaijan

• Where it goes. The tracker is hidden so that it will not be found in five minutes, and fixed rigidly to the body. Those two requirements sometimes argue with each other, and the place is chosen to suit the particular model of vehicle.
• Calibration. After fitting, the sensors are calibrated on a drive. It does not take long, but without it the calculation will be out.
• The check. The clearest test is to drive into a familiar underground car park and look at the track in Wialon. The line should carry on inside instead of stopping at the entrance. If there is no coverage underground, the track is viewed after driving out.
• The SIM card. For the city a card from any local operator will do. For vehicles that travel to Georgia or Russia a multi-operator card is better.
• Rights to send commands. If you are fitting immobilisation or a hidden buzzer, decide in advance who in the company may use them. Every command should be logged with the user's name and the time.

Choosing, in short

Not everyone needs dead reckoning. It earns its place when vehicles regularly end up where there are no satellites and when a gap in the track is expensive: rental, leasing, expensive vehicles, valuable loads, transport at risk of theft.

For a fleet that drives open roads and spends the night in a guarded yard, an ordinary tracker is enough. If you are not sure, count how many times a month your vehicles go under a roof and what you lose by not seeing them while they are there.

The equipment catalogue will help you pick a model for the fleet, and we take on the fitting and the notification settings. More on the subject: how GNSS differs from GPS and what makes up the cost of monitoring.