The purpose of the document in this series is to report upon the acquisition, processing and rendering of bathymetric survey data in support of the asset integrity multibeam survey undertaken at the Gunfleet Sands 1 & 2 Windfarm in the Thames Estuary. The survey data was collected utilising the PLA survey vessel s/v Maplin fitted with a high resolution R2Sonic 2024 multibeam echosounder operated in a single head configuration. In order to best utilise favourable tide and weather period’s, acquisition was accomplished on 13th December 2016. No H&S incidents, near misses or unsafe acts occurred during the project. The acquired and processed data was of high quality and coverage and sounding density and associated specifications set by the client were met. The scope of the GFS 01&02 survey was to survey the Offshore Substation (OSS).