Combined Multibeam and LIDAR survay 2017

A video from a survey to monitor changes in a historical structure over time. The breakwater, which is between 200 and 300 years old and stretches for two kilometres, has suffered damage during storms many times over this period. Annual surveys will create a record of the structure as it currently stands and comparisons between datasets will enable detection of sub-centimetre movements over time.

The survey combines LIDAR and Multibeam scans to produce a single model of above and below water.

Difference models show

  • Erosion (scour) or deposition of sediment.
  • Displacement of rock armour
  • Subsidence of structures
  • Ross of material.
LiDAR scans were done above water with minimum possible water level to ensure maximum survey area coverage.

Laser Scanning of:

  • Rock armour revetments
  • Vertical masonry walls
  • Masonry and concrete paved areas
  • Slipway
  • Lighthouse

Multibeam scans were done below water level, at suitable tidal level to allow overlap of results with above water laser scan survey.

Sonar Scanning of:

  • Vertical walls,
  • Slipway,
  • Rock armour revetment,
  • seabed bathymetry and features.

The surveys were compared at all locations. The comparison has been done between the original survey (2015) and the current survey, using either:

  • Point Cloud comparison (distance Cloud to Cloud)
  • Mesh comparison (After modelling the point cloud into a surface),
  • Profile section across the seabed and the structures
Teledyne Marine Equipment: 

 Credit: Hydromaster LDT

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