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Using Multibeam Technology to Detect Seabed Changes In Dynamic Environments on the West Coast of Scotland

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Introduction

In late 2020, NORBIT partnered with the Scottish Association for Marine Science (SAMS) to study the evolution of the seabed off the west coast of Scotland.

A survey was performed using the NORBIT iWBMSh integrated multibeam survey system, mounted on a vessel of opportunity. The survey was performed over the course of 2 days.

Two areas were mapped:

  • Falls of Lora (a tidal rapid)
  • Wreck of the SS Breda, sunk in 1942 in Ardmucknish Bay.

Data was acquired with NORBIT DCT and processed using Teledyne CARIS. The data was fed into signal analysis models and compared with previous data to quantify sediment movements.

Local History

Situated on the west coast of Scotland, the Falls of Lora is a tidal rapid at the mouth of Loch Etive, approximately 6 miles from Oban. It is popular with divers, kayakers and tourists.

The surrounding area contains a number of well-known ship wrecks which have become popular diving sites. Most of these wrecks sunk during the early 20th century.

The surrounding area contains a number of well-known ship wrecks which have become popular diving sites. Most of these wrecks sunk during the early 20th century.

Norbit iWBMSh

NORBIT iWBMSh benefits:

  • Frequency agile 200-700kHz.
  • 0.5 x 0.5beam width resolution at 700kHz.
  • Up to 210swath width (single head) as standard.
  • HD beamformer providing 512 beams per ping.
  • High performance integrated GNSS/INS system.
  • Integrated sound velocity probe.
  • Small form factor and low power consumption.
  • Designed for rapid mobilization on any platform.
  • Bathymetry and various backscatter and water column data as standard deliverables.
  • Optional integrated LiDAR.

For full specifications, visit www.norbit.com/subsea

Installation and Data Collection

The NORBIT iWBMSh was installed on an over-the-side pole mount and configured for
operation in less than 1 hour.

  • Line planning and data acquisition was performed on a tablet device using NORBIT’s Data Acquisition Software (DCT), a simple to use web-based interface that requires minimal setup (no complex project setups, offsets or geodetic configurations required.)
  • DCT outputs the complete sonar and navigation solution to the well-known s7k data format, which is fully supported by all hydrographic processing software packages.

Data and Results

Bathymetry data

Falls of Lora Tide Flow

Backscatter Data

Modelling Change in Seabed Topography

Sediment Displacement

Survey of the SS Breda Ship Wreck

The SS Breda was a cargo ship, 123m in length, which sank during World War II. It rests on the seabed at approximately 26m depth. The above image shows raw point cloud data collected from multiple passes over the wreck.
The above images show raw point cloud data from additional angles, collected from multiple passes. The DCT real time acquisition display is shown on the bottom left.

Produced with thanks to Christian Armstrong and Dr. John Howe at the Scottish Association for Marine Science.