Two separate acoustic survey datasets were used in the Goodwin Sands rMCZ, one acquired prior to the MCZ programme for the purposes of safety at sea, and another acquired specifically for the rMCZ. In the western sector, existing multibeam bathymetry data were used to assist in the planning and interpretation of seabed habitats. These data were collected in September 2009 as part of the UK's Civil Hydrography Programme (CHP), managed by the Maritime and Coastguard Agency (MCA). The data are archived by the United Kingdom Hydrographic Office (UKHO) and were provided to Cefas as fully processed and cleaned bathymetry data, as well as raw data files for further backscatter processing by Cefas. The bathymetric data were collected and processed in accordance with the International Hydrographic Organisation (IHO) Standards for Hydrographic Surveys - Order 1 (Special Publication 44, Edition 4). Further details on the acquisition and processing of multibeam bathymetry data can be found in HI1294 Report of Survey (2009). Processing of the backscatter data was undertaken by Cefas using the raw data provided. The software package QPS FM Geocoder Toolkit (FMGT) was used to produce fully compensated and corrected backscatter mosaic images, and these were exported as floating point geotiff files for further analysis. Both bathymetry and backscatter datasets were gridded at 2 m resolution for analysis (see Appendix 2 for images derived from acoustic data).

To cover the remainder of the rMCZ, Cefas acquired further acoustic data in April and May 2014 (Cruise code: CEND0614, Lyman et al., 2014). Processing of the acoustic data followed the same protocols as listed above for the CHP data, and the two datasets were combined into single bathymetry and backscatter floating point geotiffs gridded at 2 m resolution. Each survey achieved 100% coverage, but there remains a small, unsurveyed gap between the CHP and Cefas data (Appendix 2). There are further gaps in the data record over the Goodwin Sands banks themselves, which were periodically exposed by low tides and thus could not be surveyed. In total, 93% of the rMCZ area was surveyed.

Ground truth samples were collected during three separate surveys, two of which were conducted by Cefas in January and April/May, 2014 (Cruise code: CEND0114, Nicolaus and Ware, 2014; Cruise code: CEND0614, Lyman et al., 2014 respectively). A further inshore survey was conducted on behalf of Cefas in September/October 2014 by the Environment Agency (EA) (Project code: C5784A; Miller and Godsell, 2014).

Across the Goodwin Sands rMCZ, ground truth samples were collected from 372 stations (Figure 2; Appendix 1). A combination of physical sediment grabs and seabed imagery were acquired during each survey. Unless stated otherwise, video and still images were analysed using an established protocol developed and used by Cefas (Coggan et al., 2007). As part of the January 2014 survey, groundtruthing samples were acquired from the RV Cefas Endeavour in the deeper areas of the Goodwin Sands rMCZ following a 2 km triangular lattice grid, as there was no acoustic data available to inform site selection. Groundtruthing was achieved using sediment grabs and drop-camera (DC) video and stills at 39 stations. Sediment grabs were acquired using a 0.1 m² mini Hamon grab, and were sub-sampled for particle size analysis (PSA). Complete sediment analysis was conducted post cruise by Cefas scientists, and samples were classified into both Folk and EUNIS BSH classes. Video and stills imagery were acquired with a drop-camera (DC) system, which was deployed at all stations. Video transects lasting a minimum of 2 minutes were carried out as standard during the tow, though longer video transects (minimum 10 minutes) were carried out at a subset of stations (ca. ? of stations).

Groundtruthing samples were acquired from shallower areas of the Goodwin Sands rMCZ with site selection informed by preliminary acoustic data interpretation. Groundtruthing samples were collected at 23 stations in April/May 2014 using the same acquisition and instrument setup as described for the January 2014 survey.

Finally, during the September/October 2014 survey, groundtruthing samples were taken aboard the coastal survey vessels Thames Guardian and Solent Guardian within the inshore areas of the Goodwin Sands rMCZ. Groundtruthing was achieved using sediment grabs and drop-camera (DC) video and stills imagery at 86 stations. All the ground-truthing stations were initially surveyed using drop camera equipment (DC). A preliminary assessment of the video footage and still images collected was subsequently carried out to identify locations suitable for sediment grab deployment. Sediment grabs were acquired using a 0.1m² mini Hamon grab, and were subsampled for PSA.

All new maps and their derivatives have been based on a WGS84 datum. A new habitat map for the site was produced by analysing and interpreting the available acoustic data (as detailed above) and the ground-truth data collected by the dedicated surveys of this site. The process is a combination of two approaches, auto-classification (image analysis) and expert interpretation. The routine for auto-classification is flexible and dependent on site-specific data, allowing for application of a bespoke routine to maximise the acoustic data available. ArcGIS was used to perform an initial unsupervised classification on the backscatter image. The single-band backscatter mosaic was filtered and smoothed prior to the application of an Iso cluster/maximum likelihood classification routine. Python scripting language was used to automate the workflow.