AusCoastVDT is an easy to use vertical datum transformation tool for the Australian coast. Despite the data limitations discovered in the Project 3 research (Vertical datum transformations across the littoral zone), a broad range of coastal applications are increasingly demanding seamless coastal elevation data.
Hence the Intergovernmental Committee on Surveying and Mapping (ICSM) Permanent Committee on Tides and Mean Sea Level (PCTMSL) supported the development of this vertical datum transformation tool using coarse data available at the time.
AusCoastVDT and the supplied vertical separation grid initially provide national coverage at a coarse level (the supplied grid has a cell size of 1 minute of arc or ~1.8km depending on latitude), and the grid will be improved in high priority areas, via focused efforts to collect additional data.
A very conservative estimate of the accuracy of the tidal separations would be ±0.5m in the vertical and ±1km horizontally. Even though the accuracy of the transformation may be weak in parts of Australia it provides an easy mechanism for organisations to start tackling the issue of data integration.
It should be noted that the AHS and ICSM PCTMSL considers the supplied vertical separation grid to be “experimental” and “unsupported” until further work can be done to help verify/improve the method of creation and further determine/improve the accuracy of the grid. There are a number of limitations to consider with regard to the accuracy of the grid and its transformations which are detailed in the user manual and disclaimer.
The tool includes transformations between data referenced to the GRS80 ellipsoid (realised through GDA94), Lowest Astronomical Tide (LAT), MSL, the Australian Height Datum (AHD), Highest Astronomical Tide (HAT) and other vertical datums of user interest (and vice versa).
AusCoastVDT provides file-based vertical transformations via a vertical separation grid file or a block shift, and geographic point based transformations (typed or map click) via a vertical separation grid file (figure 1). A coarse vertical separation grid file with fifteen reference surfaces is provided in the tool, along with the capability for users to supply alternative vertical separation grids. The applicable area of the supplied vertical separation grid (figure 2) is from approximately 20km inland of the coastline to approximately the 500m bathymetric contour.
The key applications driving the development of this tool and the facilitation of seamless coastal elevation datasets are studying the impacts of sea level rise and storm surge inundation modelling. Other applications benefiting include tsunami inundation modelling, coastal zone management, marine boundary delimitation, habitat restoration, erosion studies, coastal ecosystem modelling, beach renourishment projects, coastal construction and development, shoreline change analysis, as well as building and maintaining the national DEM.
The AusCoastVDT tool and coarse vertical separation grid can be downloaded from the ICSM PCTMSL website along with installation instructions.