Muddy waters, strong currents and restricted visibility are everyday challenges in underwater inspections of bridges. The founders of VRT, civil engineers Olli Auer and Kirsi Hänninen, started their careers with bridge inspections, repair and new bridge planning 15 years ago.

“The diving inspections are great when material samples or closer check-ups are needed. But the overall inspection of bridge’s underwater parts… Well, I used to watch quite a lot of blurry diver videos or rough reports about the findings”, Olli Auer recalls the years before VRT.

The idea of a better way for bridge inspections rose from the innovative minds of the two engineers, and soon it was time to start their own company.

Cooperation with Finnish authorities

VRT was founded in 2010, and it was a trailblazer in bridge inspection field. For the first time the sonar scanners were used to scan vertical structures instead of seabed.

“From the first years on we did hundreds of bridge inspections, because we had strong experience in bridge design and inspections. We soon realized that the instructions for underwater inspections were from the old days when diving was the only option to see the underwater structures”, Auer describes the starting point of VRT.

VRT participated in a working group Finnish Transport Agency (now FTIA) started in quest for updating the instructions to match the modern technology. The instructions were published in 2016, and they included also sonar scanning as the approved methodology.

The advantages of sonar scanning in bridge inspections

Sonar inspections are still surprisingly uncommon in bridge engineering world. Many countries’ public authorities responsible for transport still rely on diving, even though the sonar technology has many advantages. When talking about critical underwater structures, such as bridges, it is important to have a detailed and comprehensive picture of both the structure and the area around it. Erosion or exposed foundation slabs effect the bridge’s life cycle, as well as damages in piers or bearings.

“Planning is done in 3D almost everywhere in the world these days, and with multibeam sonar inspections you get also the survey data in 3D”, Auer points out.

Whether you compare the as-built situation to plans or plan the repairs -3D data is useful in every part of the bridge’s life cycle.

Sonar scanning is a cost-effective and safe way of performing underwater inspections, and VRT offers the whole service in-house. Rivers often have strong currents, where an agile survey vessel and an experienced skipper are priceless, allowing safe and swift surveys. The 3D data gathered from the survey is post-processed and analyzed by our professional inspectors trained by FTIA, and reporting is conveniently done via 3D online platform GISGRO.

With the experience from hundreds of bridge inspections, we would love to help you in planning bridges’ life cycle management. Contact our specialist to discuss the topic in more detail and step to the world of easier bridge maintenance!

Contact us

Interested in our services? Contact us!

Karri Kolehmainen & Ville Mäkeläinen

Karri Koistinen

+358 40 0604927



Ville Mäkeläinen

+358 44 513 2222


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