Underwater infrastructures are made visible by multibeam sonar survey, but the interpretation of the survey data requires a trained professional. VRT Finland Ltd. has a team of certified inspectors, who analyze the structures and the severity of damaging. The locations needing attention are highlighted in the inspection report.

The inspector uses several sources of information

The surveyed point cloud data is the starting point of the inspection, but our inspectors use also other information for piecing together the complete story of the structures.

“The inspector looks at the condition of the infrastructures and their surroundings as they are. Providing background information, such as construction or repair works planned or performed before, is helpful. That places the observations on a timeline – the life cycle of the structure. Identifying the areas of interest and the purpose of the inspection adds depth and value to what is normally a general inspection underwater”, Henriikka Keskinen, Head of Analysis, defines the starting point of the structural inspection.

Our inspectors are based at Jyväskylä headquarters and aren’t always able to visit the survey site themselves. The 3D survey data and the observations made by the field team of surveyors, combined with photographs and plans form a coherent picture, based on which the inspector performs the work. The point cloud data is uploaded to GISGRO, where the inspector defines the inspection area, adds measurements, and sees to the visual presentation, such as setting the colors indicating depth. The whole inspection area is examined in detail.

“It’s detective work. You could, for example, notice a small crack above the waterline, which is connected to more extensive deformation underwater. Upon further analysis we could find that the deflection in the quay wall has been caused by a crane on the quay being too heavy. You no longer have individual observations, but a story of cause and effect. Using the analysis tools in GISGRO allows us to verify and report findings”, Keskinen explains.

Valuable information for asset maintenance and budgeting

GISGRO, the 3D online platform, has facilitated the work of inspectors by replacing multiple software used in the analysis and reporting. All the observations are made directly into the 3D data with global coordinates. GISGRO composes a PDF report of the observations automatically, which can be downloaded from the platform.

“We performed the surveys and the inspections in 3D before GISGRO as well, but the deliverables the customer received were generally in 2D only. With the 3D point cloud models in GISGRO, the amount of information that can be extracted from the survey data is manifold. We’ve received good feedback about GISGRO, especially from those responsible for budgeting and procuring funding for maintenance. They feel like they have more data to base important decisions on”, Keskinen describes the value of 3D reporting.

Analyzing different materials and structures requires structural knowhow. The VRT inspectors are civil engineers and architects by background.

“The inspector might be the first one ever to take a look at the structure underwater, since it was built. It is rewarding to introduce the findings to the customers and get the story completed”, Keskinen concludes.

If you want an expert’s evaluation on the condition of underwater structures, contact us via the form below.


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Karri Kolehmainen & Ville Mäkeläinen

Karri Koistinen

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