A consortium comprising of the R&D UK Centre of EDF Energy, UTEC (an Acteon company), and Partrac Ltd completed an offshore trial designed to assess the performance of a commercial Autonomous Underwater Vehicle (AUV) for mapping seabed bathymetry. The trial was performed at EDF Renewables Teesside Offshore Wind Farm located off the North Yorkshire coast in England. The project tested a Teledyne Gavia Surveyor AUV owned and operated by global survey firm UTEC. Newcastle-based marine consultants Partrac Ltd provided support with survey area selection and critical appraisal of the AUV survey datasets.
The aim of the trial was to determine if AUV’s could replace traditional vessel based surveys, given that in recent years, the utilisation of AUV’s has increased significantly. AUV advancements have mainly been in the technology of system sensors and batteries which has presented opportunities for manufacturers to be able to compete with traditional (vessel-based) acquisition techniques both in terms of cost and quality for a range of applications. However, as datasets have rarely been compared in a rigorous fashion, the trial intends to address this by performing an in-depth comparison between the bathymetric data from a vessel and from an AUV collected at several target areas within the boundary of Teesside Offshore Wind Farm.
Survey operations to collect the data were undertaken in August-September 2017, at the Teesside Offshore Wind Farm site, where areas of pronounced bed topography (scour protection), smooth areas of seabed and part of the export cable route, in approximately 30m water depth, were covered by two different vessels, one running a Reson 8125H MBES and a second equipped with a Reson SeaBat 7125 SV2 MBES. The Gavia, equipped with a Kongsberg GeoSwath interferometric echo sounder, covered the same ground.
Following an in-depth review of the datasets, it was concluded that the AUV technology offers certain advantages in terms of logistics, operable weather windows etc. and may be particularly suited to assessing marine scour; The study also provided a series of recommendations for future use of the AUV technology for bathymetry mapping, across the areas of data quality, positioning, vertical reduction, and data output formats.
Fig1: Retrieval of the AUV
Trevor Pugh, UTEC Technical Authority said: “The primary objective was to prove that AUV bathymetry data quality matches vessel data. However, we were also able to demonstrate the low logistic requirements of the Gavia in that it was launched and recovered from the Crew Transfer Vessel as it does not need the dedicated launch and recovery systems needed for larger AUV’s or ROV’s.
Kevin Black from Partrac said:” The trial provided a proving ground for evaluation of the AUV technology in a systematic way and at a real offshore wind farm site; the findings certainly support the case for using AUV’s for coastal survey”.
Hugo Herrmann, from the EDF Energy R&D UKC said:” This collaborative work between EDF, UTEC and Partrac demonstrated the great potential of using AUV’s in comparison to traditional vessel based surveys."
Karl Burns from EDF Renewables, said: “After this initial trial, we are now looking at what steps are required to deploy an AUV in the offshore operational environment.”
The assistance of PD Teesport’s Survey Department and the provision of one of the vessel-based survey datasets is gratefully acknowledged.