Struggling with the laboriousness and fuzzy view of diver inspections, the founders of VRT decided to invent a better way for underwater structural inspections. Already in 2010, the first sonar structural inspections were performed, and the technology has been improving since.

Diver inspections are handy when you need to get detailed information of one certain spot or area. But when dealing with large areas and demanding high accuracy, whether the structure is a long quay, bridge or pipeline in the lake, it is more cost effective to use mobile mapping system.

Benefits of multibeam sonar inspections

Underwater structures’ inspections often include challenges from murky water, busy traffic or strong currents. Multibeam sonar offers answers to these challenges and easies the maintenance of underwater assets.


Multibeam sonar is based on the measurements of sound waves. Sound pulses (also called pings) bounce back from an object and the distance can be calculated when the exact location of the emitter is known. VRT survey vessels record GNSS RTK positioning data, which is further post-processed at the office to achieve the position accuracy of few centimeters.

Particles in the water can totally block the view of a diver, but from the multibeam sonar data the error points caused by the particles are cleaned in the post-processing phase to make a crystal-clear picture of the structure. The 3D model reveals the overall condition of the structure and can be zoomed into the tiniest details.


Using an agile survey vessel minimizes the time spent to the field work. The time depends on the structure’s type and depth of the water, for example 1,5 kilometers of quay structures, 5-10 kilometers of pipeline or up to 20 bridge piers can be scanned in a day. Our survey engineers have the skills to plan the survey safely and efficiently even in the busiest ports and strong currents, so that the data is premium despite the circumstances. Also, laser or drone (photogrammetry) data from above the waterline can be combined to the 3D model, our fleet includes all these mobile scanning technologies.


Working with the pioneers of the field of underwater inspections make sure that the whole process in carried out professionally. Basically, all you need to know is what structures you want to have inspected. Our sales team discusses the methods and timetable with the survey team, they agree the suitable field days with you and our office team does the rest, delivering the final 3D data in an easy-to-use online platform. You get a full report of the observations and even a hand-out meeting with the inspector.


We have gathered information about underwater inspections, 3D data utilization and asset management into Quick Guides. You can download all the guides here. If you want to discuss in more detail about your inspection needs, contact our specialists or leave a request for quote.

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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