Data Coverage Statistics [18] Figures 2f–2h show the relative data coverage for the Gulf of Papua, GEBCO and ETOPO2 grids, respective- ly. Minor differences occur in the different ship track data sets; however, the Gulf of Papua grid benefits from the addition of multibeam, hydrographic data sets, digitized charts and bathymetry derived from Landsat (Figures 2a, 2b, 2d, and 2e). The total number of data points used in the Gulf of Papua grid (when reduced to a 3.600 grid) is 9.1 106. By comparison, ETOPO2 has 1.5 105 data points for the same area. No comparison is made with the GEBCO data set as ship tracks are supplied without bathymetry (i.e., navigation only). [19] Key statistics for each data set used in the construc- tion of the bathymetric grid are shown in Table 4. In the marine zone, 19.3% of grid cells had associated bathymetric soundings or Landsat-derived bathymetry, 59.8% of the final data set was multibeam bathymetry, 23.4% was Land- sat-derived, and 10.9% was provided by the Australian Hydrographic Service.