Multi-Beam Echo-Sounder (MBES) and mobile laser scan surveys have been successfully carried out using USV''s in Wales to assess the scour extents at the foundations of multiple structures and to provide additional information on the structures above surface.

Conwy bridge

Unmanned Survey Solutions carried out USV survey work at locations including Conwy bridge. Photo: Unmanned Survey Solutions

Unmanned Survey Solutions (USS) used two USV's to undertake the survey work at Conwy quay wall, Conwy bridge, Conwy cob and Tal Y Cafn bridge structures located within Conwy River, as commissioned by Conwy County Borough Council.

James Williams, director at USS, commented: "We conducted the survey during some of the highest tides of the year so that we could get the vessels into the shallow locations required to complete the works, however this meant we had to deploy and recover the USV’s in fast flowing waters and then undertake the surveys during the limited slack water period over the high tides."

The majority of the survey operations were undertaken in Conwy Harbour using the Accession 350 USV with survey payload consisting of an R2SONIC 2024 MBES, SBG Apogee Navsight INS, Carlson Merlin mobile laser scanner, Valeport SV sensors and Hypack Hysweep data acquisition and post processing software.

The Tal Y Cafn bridge was located further up Conwy River and required an alternative smaller USV solution due to the shallow water depths and vessel launching restrictions. At this location an Inception MKII USV with SONIC 2020 MBES, SBG Ekinox-D INS, Valeport SV sensors and Hypack Hysweep software was selected due to its portability and ease of launch.

Challenges included fast flowing currents, varying depths, numerous mooring buoys and limited operational windows of only 2.5 hours per high tide to survey all locations.

By Rebecca Jeffrey