A coastline polygon was created from the 2011 digital elevation model (DEM) by Geoscience Australia using ArcMap. First, all the DEM pixels were reclassified using the ‘reclassify’ tool to give the value of zero, then using the ‘raster to polygon tool’ the coastline was generated. When compared to the 1:30,000 coastline, and the 2011 orthophotography, the accuracy is variable. As the LiDAR survey was conducted in some locations at low tide, the 2011 outline may include areas that are not actually considered island, such as sandbanks in shallow lagoon areas. The 2011 coastline does not follow the edge of ‘land’ as closely compared to the 2010 version in areas with extensive sand flats. The zero elevation level for survey used the CKIHD. The closure of the North Keeling lagoon is clear between the datasets.