Photo credit (banner): Alex Profit

How we track our trains

Want to track your train in real time? That’s why we created the SNCF Maps tool, accessible at But it takes a sophisticated mix of many high-tech tools to share this up-to-the-minute geolocation data. Here’s how it works.

Track SNCF trains in real time

Published on | Updated on

5-minute read

When an SNCF train runs on the rail network in France, you can find its location in three ways:

  • visit our website, choose Itinerary & booking and click on “Our trains in real time”
  • access our “on-board Internet” service from your TGV INOUI train

To identify the exact location of each train, we use data compiled by our SNCF Maps tool. It creates a “flight radar map” that tracks rail traffic in real time, in much the same way as “moving maps” on long-haul flights.

Though geolocation is useful for any number of internal rail operations, we created SNCF Maps just for you, partnering with mobility software specialist HaCon to make it available to all SNCF passengers.

Access SNCF Maps

A mix of technologies

SNCF Maps combines several different systems to deliver high-precision geolocation data:

  • mapping tools
  • train positioning tools
  • the exact route of your train

Each of these components has its own set of technologies and software packages, but they also rely on servers that communicate with each other, gathering data from a variety of sources and putting it all together.

How we pinpoint each train’s position

Identifying the exact position of each train is essential to the geolocation process. For that, we use our Géomobiles app, which aggregates the locations of all SNCF trains—TGV, TGV INOUI, TER, Intercités and OUIGO

Géomobiles also relies on a mix of very different systems that communicate with modems, software, individual manufacturers and more. Through the magic of technology, data from all of these sources is assembled in a single database, which supplies information to SNCF Maps.

  • 10

    million data points are sent to Géomobiles every day

  • 15,000 rail journeys processed daily

Sensors on infrastructures and aboard trains

To stay in constant contact with every SNCF train operating on our network, Géomobiles pools data from three groups of sensors:

  • Bréhat “official” sensors on network infrastructures, which are triggered as each train passes
  • GPS Trains sensors on the roof of each train, which supply positioning data via satellite
  • Sirius tablets used by SNCF train drivers, which emit signals at regular intervals, showing each train’s location

Bréhat “official” sensors

Bréhat sensors are installed on the tracks throughout the SNCF network. We’ve used them for decades to manage traffic, and their data are the legal record.

This means that when a train is delayed, the time and position data from the Bréhat system is authoritative under the law. It’s essential for this benchmark to come from the network infrastructure—which is neutral—rather than the network operator.

As a result, geolocation data from Géomobiles, which comes from a variety of sources, has no legal value and is solely for the convenience of our customers.

Why we use “hot” and “cold” data

To get a reliable picture of the network

To display the movements of our trains and identify any disruptions, we use information from two sources: our transport plan and data from Géomobiles.

For example, if a train is scheduled to depart from Paris Nord station at 9.16 and reach Lille-Flandres at 10.22, that’s “cold”—or theoretical—data from our transport plan.

SNCF Maps compares this cold data to “hot”—or real-time—train geolocation data from Géomobiles to determine whether there’s any disruption, such as a delay or an unscheduled stop. It then displays that information, so you can track your train and stay up to date on service disruptions.

How we plot the exact route of each train

We also use Géomobiles data to show you each train’s route in SNCF Maps.

Unlike the images on a GPS system, trains don’t run in straight lines. Their exact route depends on many variables, including the type of rolling stock, the rails, and the train path1 they’re assigned to.

Here again, SNCF Maps compares all of the cold information from the rail network to hot, real-time data to give you the train’s route with extreme accuracy.

Result: when you connect to the WiFi portal aboard a TGV INOUI, you can follow your train’s progress across the map of France in real time.

Learn more about the TGV INOUI WiFi portal

Before the revolution

Before the advent of digital technology, rail traffic controllers reported train movements to help manage traffic on the network—and they were the only ones who knew where the trains where.

Each controller was responsible for pooling time and location data and phoning it in to station masters.

In stark contrast to today’s digital tools, controllers worked on paper traffic charts and drew routes with rulers.

1A train path is the infrastructure capacity needed to run a train on a given route on a given timetable—in other words, the time period during which a given infrastructure is assigned to a train running between two points on the rail network.