A coastline polygon was created from the 2011 digital elevation model (DEM) by Geoscience Australia using ArcMap. When compared to the 2010 coastline (1:30,000 data), and the 2011 orthophotography, the 2011 coastline follows the actual coast more accurately. To make the coastline, all the DEM pixels were reclassified using the ‘reclassify’ tool to give the value of zero, then the coastline was generated using the ‘raster to polygon tool’.
Notes on other coast outlines:
Cadastre coastline: The coastline displayed as part of the cadastre is derived from the 1999 coastline, as well as some sections which have been manually surveyed.
1999 coastline: A digital elevation model of Christmas Island was created in 1999 from which a coastline was created. This is presumed to be the basis of the 1:25,000 coastline and the original 1:30,000 coastline.