| Summary: | Progress Code: completed Statement: The data processing was undertaken using ESRI ArcGIS ArcInfo 8.3 software. Bathymetric contours with depth a multiple of 500 m were extracted from the GEBCO 2003 data as a shapefile. The data were projected to a Polar Stereographic Projection (Latitude of True Scale 71 degrees South). The data were clipped to the required mapping extent, converted to a double precision coverage, and cleaned with a dangle length of 150 m to resolve the minor dangles associated with the arcs. The data were then checked for dangles. Dangle errors were either arc undershoots or overshoots. Overshoots were deleted, whilst connectors were added to join and complete arcs, which were undershoots. Once the dangle errors were resolved the data were cleaned with a dangle length of 5m and checked to ensure all dangles, except those round the Antarctic Coastline, had been resolved. The coastline from the Antarctic Digital Database, version 4 scale of capture data, was then integrated with the bathymetry. The integrated coverage was again cleaned, this time with a small tolerance of 0.25 m. The dangles associated with the integration of the coastline were then resolved. As before overshoots were deleted, whilst connectors were added to join and complete arcs, which were undershoots. A depth of 0m was assigned to the Antarctic coastline arcs. The integrated dataset was built for arcs and polygons. Minimum and maximum depth attribute values were then assigned to all polygons. The difference in these values was usually either 0m or 500m. (The difference is 0m if a polygon is comprised of arcs of the same depth, in other words a closed loop). If the difference differed from either 0m or 500m the polygons were tagged and checked. There are a number of cases where the entire required GEBCO bathymetric contour does not exist. For example a 2000m contour line may be missing, and hence a polygon has a depth range of 1000m (from 1500m to 2500m). These were deemed to be valid values. Once the final checks were ...
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