Bathymetry of Approaches to Casey Station

Full description

Bathymetric Contours and height range polygons of approaches to Casey Station, derived from RAN Fair sheet, Aurora Australis and GEBCO soundings.

Lineage

Progress Code: completed

Statement: All the soundings from three RAN fair Sheets were digitised as points using Microstation. The fair sheets used were Approaches to Casey - Sheets HI 161 V5/500-6610/1 Scale 1:10 000 HI 161 V5/500-6610/2 Scale 1:25 000 HI 189 V5/584 Scale 1:25 000 Centre of gravity of the text was regarded as point position. The points from each sheet were assigned the relevant Data Quality Indicator and merged into a single dataset. The data were then converted to ArcInfo format and merged with GEBCO 97 data and Aurora Australis data supplied by the Australian Antarctic Data Centre. DQI Regions and contours were generated from the resulting merged data set. Contouring was performed using Intergraph's Siteworks. The contour interval was 5 metres in areas of scale 1:10 000 to 1:25 000 and 50-200 metres in areas of much smaller scale (GEBCO and Aurora Australis). Resulting contour lines were converted to ArcInfo format and checked for overlapping lines. These were fixed where they occurred. The ends of the contours were closed using connectors and the resulting data set was built for polygons. The contour height values were transferred to the polygon tables. Depressions were determined by isolating closed polygons (without connectors); if these contained contours which went below the height range of the surrounding contours then they were tagged as depressions. Feature values for polygons were also determined from their surrounding lines. The final data set was subdivided into Data Quality Indicator (DQI) regions so that the polygons and arcs could be tagged with the correct DQI value. DQI regions were assigned using the bounds of the most accurate data set first and then working out to the least accurate data set.