Grand Paris Express : railway inspection by chains inclinometer system

Railway inspection by Cementys for a construction site of Le Grand Paris Express project, using the chains inclinometer system.
Context and Objectives

As part of “Le Grand Paris Express line 15, section T2C” project, Cementys undertook an inspection mission of the SNCF railways by chains inclinometer system.

The aim of this inspection system is to guarantee the durability of the site for a short and long period, to control the impact of the works and to alert in case of abnormal changes and/or safety issues.

To avoid any problems related to parked trains, climate hazards, measurements frequencies… we propose a methodology for monitoring SNCF tracks in interface with the work on the OA808 branch line using chained inclinometers.

This is an alternative method to the topographical method which has been in place for the last two years. This monitoring system has the advantage of being unaffected by the weather, but also requires less maintenance than the “classic” theodolite system.

Railway inspection chains inclinometer Cementys

Chains inclinometer system

Task description

The OA808P is located at Villiers-sur-Marne, near the SNCF railways.

Nature of work : molded walls and tunnel branch works

Cementys aucultation ferroviaire inclinomètres chaînés plan

Work Plan

System Presentation

The system consists of dual-axis TiltLog inclinometers designed for track monitoring.

Sensor type : 3D-MEMS bi-axial inclinometer with a 3D positioning MEMS correction.

Sensors were placed on concrete ties by gluing system and wooden ties by riveting. They are link to a wire system and connected to a data acquisition unit. A wireless system is also available for future installations. 


Sensor : bi-axial Tiltlog 


The bi-axial TiltLog sensors enable to measure both crosswise and longitudinal angle. The measurement frequencies are less than 5 minutes. 

The angular displacements measurements of each sensor are used for railway calculation.

  • Failing deviation
  • Left
  • Longitudinal leveling
Cementys aucultation ferroviaire mesures angulaires

Pattern of angular measures

Track Geometry

Data Processing and Visualization

A real-time data processing system has been developed by the Cementys data team.

However, a thermal correction must be applied to compensate for the temperature’s reversible effect.

Abnormal measurements due to train passages must be eliminated.


Cementys aucultation ferroviaire mesures

Measures to take thermal corrections into account


The data quality is demonstrated.

The railway monitoring solution using chain inclinometer systems offers a real advantage for high-frequency measurement. These allow an early warning when thresholds are exceeded. If necessary, traffic can be stopped as quickly as possible.