Roadscanners on Railways

Roadscanners has extensive experience in assisting railway authorities and companies inspect the status of their track structures. Since 2003 Roadscanners has successfully conducted railway GPR surveys on over 40 000 track kilometers including large networks in North America, Europe and Africa.

On railways the main focus of the company’s activities has been GPR aided structural and functional condition analysis as well as problem diagnosis using integrated data analysis methods.


Information About the Railway Structures

The Ground Penetrating Radar

The Ground Penetrating Radar (GPR) method efficiently and non-destructively provides continuous information concerning the thickness of the railway structures such as the ballast, sub-ballast and embankment Layers. Structural conditions like ballast fouling and mud pumping in addition to the moisture content and water retention characteristics of the granular layers can also be analyzed from the data.

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2D & 3D GPR Surveys

The GPR surveys can be done either with a traditional two dimensional (2D) GPR system, optimal for network level surveys, or a three dimensional (3D) GPR when more detailed information is needed. The 3D GPR mapping provides both longitudinal and cross-sectional in-formation of the railway structures while a 2D survey provides information from maximum of three parallel lines. Along with the structure thickness and quality, both GPR systems provide detailed information concerning structural anomalies in the ballast bed such as settlements and ballast pockets.

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Collecting Data

The measurements are conducted at a maximum speed of 160 km/h using railway engine or 50 km/h with a hi-rail vehicle. Information about the track environment and measurement location including track video, laser scanner cross-sections and GPS coordinates are also collected simultaneously with the GPR measurements using Road Doctor® CamLink software.

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Ballast and Structure Quality Inspection

Ballast Fouling Classification Method

Together with the Finnish Transport Agency and the Technical University of Tampere Roadscanners has developed a ballast fouling classification method. A continuous fouling condition profile of the ballast bed is produced using a calibrated GPR fouling index.

The clean and fouled ballast can be distinguished and classified using the GPR data. This method is based on an analysis of the frequency information from the GPR signal. Costs are reduced when ballast cleaning is planned and focused on those sections that really need it. After classification, statistical information from each track section can also be calculated.

Additionally, quality and thickness of structures following new construction or rehabilitation measures can be inspected effectively using the GPR technique.

Results can be reviewed interactively, by a client or colleague, using Road Doctor Viewer software available free of charge at:


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