Methodology:

The bathymetry map was compiled from a variety of different data sources. The primary data are multibeam swath bathymetry collected from scientific cruises undertaken by British Antarctic Survey (BAS), Alfred Wegener Institute (AWI) and Center for Marine and Environmental Sciences (MARUM), University of Bremen. This is supplemented by older data from a BAS towed sonar survey (MR1) and single-beam data collected by previous BAS ships and commercial fishing vessels. Where no data existed from these sources, global compilations from the General Bathymetric Chart of the Oceans (GEBCO) and, below 60 South, the International Bathymetric Chart of the Southern Ocean (IBCSO) were used; both these data sets use satellite altimetry in areas where data are sparse.

The new digital elevation model was gridded in a similar way to previous grids (Fretwell et al. 2008, Dickens et al. 2014). Gridded datasets were resampled to 200 m resolution and then converted to point data. These points were then given a quality hierarchy; multibeam swath being the highest, then towed data, singlebeam and finally gridded GEBCO and IBSCO data. The data were then re-gridded using the Topogrid algorithm in ArcGIS using the hierarchy to prioritize the data. The resulting grid was then checked for errors such as spikes and holes. Where identified, these were removed from the point datasets and the data were re-gridded. This iterative process was conducted until a clean combined dataset was produced.

On land raw ASTER GDEM grids were cleaned and merged with pre-existing survey data to create new digital elevation models and supplemented by coastlines and form-lines taken from archival sketch-maps to produce a full hypsometric elevation model for each island. The bathymetry and elevation dataset was merged and gridded using ArcGIS 10.

Data collection:

The bathymetric compilation was constructed in ArcGIS 10.0 using a hierarchical system of data priority, gridded using the Topogrid function and cleaned using both manual and semi-automated methods. This was then merged with terrestrial elevations constructed from cleaned raw ASTER GDEM grids supplemented by coastlines and form-lines taken from archival sketch-maps to produce a full hypsometric elevation model.

Data sources and hierarchy

1. BAS multibeam

2. AWI multibeam

3. MARUM multibeam

4. ASTER gdem

5. Coastline vector data

6. BAS MR1 towed

7. Fisheries singlebeam

8. BAS single beam

9. IBSCO gridded data

10. GEBCO gridded data