Topography of Australia’s Intertidal Zone Available as Open Data


The National Intertidal Digital Elevation Model (NIDEM) is the first 3D model of Australia’s intertidal zone.  The dataset was built using thirty years of earth observation (EO) data and covers 15,387 km2 of intertidal terrain across Australia’s coastline.  Researchers used the 30-year time series archive of spatially and spectrally calibrated Landsat satellite data to develop the 25-meter resolution NIDEM.

Boundaries of each (a) ten percent interval of the observed tidal range from ITEM v2.0 (colours from blue to red indicate pixels inundated at increasingly high tide) were used to (b) extract contours depicting the typical location of the land-water boundary across the 30-year Landsat time series. These contours were assigned the median of all modelled tide heights attributed to the ensemble of Landsat images used to generate each tidal interval. The resulting tidally-tagged contours were used to generate (c) continuous elevation surfaces using triangulated irregular network (TIN) interpolation.

Boundaries of each (a) ten percent interval of the observed tidal range from ITEM v2.0 (colours from blue to red indicate pixels inundated at increasingly high tide) were used to (b) extract contours depicting the typical location of the land-water boundary across the 30-year Landsat time series. These contours were assigned the median of all modelled tide heights attributed to the ensemble of Landsat images used to generate each tidal interval. The resulting tidally-tagged contours were used to generate (c) continuous elevation surfaces using triangulated irregular network (TIN) interpolation. Figure: Bishop-Taylor et al., 2019

NIDEM was validated against LiDAR, RTK GPS and multibeam bathymetry datasets.  Researchers found that the dataset was “highly accurate across sandy beach (±0.41 m RMSE) and tidal flat environments (±0.39 m RMSE). Model performance was least accurate (±2.98 m RMSE) within rocky shores and reefs and other complex coastal environments with extreme and variable tidal regimes.”

The methodology for developing NIDEM has been published as an open access article in Estuarine, Coastal and Shelf Science:

Bishop-Taylor, R., Sagar, S., Lymburner, L., & Beaman, R. J. (2019). Between the tides: Modelling the elevation of Australia’s exposed intertidal zone at continental scale. Estuarine, Coastal and Shelf Science. https://doi.org/10.1016/j.ecss.2019.03.006

The data can be accessed via Australia’s National Map portal.


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