Document Title - Geoscience Australia

Lord Howe High Resolution Grids
Figure 6: AHS chart data covering both the Lord Howe Island and Ball’s Pyramid region.
Chart data
In recent years the AHS has undertaken the major task of digitising its large collection of
bathymetric charts. Under a memorandum of understanding (MOU) GA now has access to much of
these data.
Two independent sets of chart data exist: one collected by the Australian Navy; the other by National
Mapping. The digitised values taken from the charts were obtained via the University of
Wollongong which maintains a GIS of Lord Howe bathymetry.
The Navy data were collected circa 1959 and the National Mapping data circa 1984. Both datasets
have been converted to mean sea level (MSL) and WGS84. Many of the depths when overlaid on
chart AUS610 (http://www.hydro.gov.au/webapps/jsp/charts/charts.jsp?chart=Aus610&subchart=0)
match up, which indicates that the digitising process has been reliably conducted. The stated
positional accuracy of the chart is anywhere from 5 m to 500 m. More information on these datasets
can be found in Dickson et al. (2002). The data distribution of both the Navy and National Mapping
chart data are shown in Figure 6.
10