source: production/pt_hedland_2006/report/data.tex @ 3365

The calculated run-up height and resulting inundation ashore is determined by
the input topographic and bathymetric elevation, the forcing terms, the
initial and boundary conditions, as well as the cell area of the computational
mesh. 
Ideally, the data should adequately capture all complex features
of the underlying bathymetry and topography. Any limitations
in the resolution and accuracy of the data will introduce 
errors to the inundation maps, in addition to the range of approximations
made within the model.

Data for this study have been sourced from a number of agencies. With
respect to the onshore data, the Defence Imagery and Geospatial
Organisation (DIGO) supplied the Digital Terrain Elevation
Data Level 2 (DTED) which has been authorised for Australian Tsunami
Warning System use only. The resolution of this data is 1 second
(about 30 metres), and has been produced from 1:50 000 contours, elevations and
drainage. In addition, the Department of Land Information (DLI) has provided a
20m Digital Elevation Model (DEM) and orthophotography 
covering the NW Shelf. The DTED Level 2 data is ``bare earth'' and
the DLI data distorted by vegetation and buildings.  

Figure \ref{fig:contours_compare}(a) shows the contour lines for
HAT, MSL and LAT for Port Hedland using the DTED data where it is evident 
that the extent of the tidal inundation is exaggerated. This is due to
short comings with the digital elevation model (DEM) created from 
the DTED data. 
Figure \ref{fig:contours_compare}(b) shows
the contour lines for HAT, MSL and LAT for Port Hedland using the WA DLI data.
It is obvious that there are significant differences in each DEM with
total station survey information and the knowledge
of the HAT contour line pointing to increased confidence in the WA DLI
data over the DTED data for use in the inundation modelling.
The impact difference based on these two onshore data sets 
will be discussed in Section \ref{sec:issues}.


\begin{figure}[p]
\center{(a)}
  \centerline{ \includegraphics[width=150mm, height=100mm]
{../report_figures/pt_hedland_dted_contour.jpg}}

 % \caption{Port Hedland region showing the -3.9m AHD (LAT), 0m AHD (MSL)
 %and -3.6m AHD (LAT) contour lines using the DTED Level 2 data.}
 % \label{fig:contours_dted}
%\end{figure}

%\begin{figure}[hbt]
\center{(b)}
  \centerline{ \includegraphics[width=150mm, height=100mm]
{../report_figures/pt_hedland_dli_contour.jpg}}

  \caption{Port Hedland region showing the -3.9m AHD (LAT), 0m AHD (MSL) 
and 3.6m AHD (HAT) contour lines using the (a) DTED Level 2 data and
the (b) WA DLI data.}
 % \label{fig:contours_dli}
 \label{fig:contours_compare}
\end{figure}

With respect to the offshore data, the Department of Planning and
Infrastructure (DPI) have provided state digital fairsheet data around
Port Hedland. This data cover only a very small geographic area. (Note,
similar data have been provided by DPI for Onslow and Broome.) 
The Australian Hydrographic Office (AHO) has supplied extensive
fairsheet data which has also been utilised. In contrast to the onshore data, the offshore data is a series of survey points which is typically not supplied on a fixed grid. In addition, offshore data typically does not have the coverage of the onshore data, and often the offshore data will have gaps where surveys have not been conducted.
The coastline has been generated by
using the aerial photography and two detailed surveys provided
by WA DPI. 
The WA DLI data surrounding the coast are error prone and
have been clipped at the derived coastline. 
Appendix \ref{sec:metadata} provides more details and the supporting metadata 
for this study.
Table \ref{table:data} summarises the available data for this study. 
Figure \ref{fig:pthedlanddataarea} shows the offshore data indicating a number of gaps.

\begin{table}
\caption{Available data for the North West shelf tsunami inundation studies.}
\label{table:data}
\begin{center}
\begin{tabular}{|l|l|}\hline
Data & Detail \\ \hline 
DIGO DTED Level 2  & Onshore, 1 second $\approx$ 30m \\ \hline 
DLI & Onshore, 20m DEM and orthophotography \\ \hline
DPI & Offshore, fairsheet data around Port Hedland \\ \hline
AHO & Offshore, fairsheet data for North West Shelf region \\ \hline
\end{tabular}
\end{center}
\end{table}

\begin{figure}[hbt]

  \centerline{ \includegraphics[width=100mm, height=75mm]
{../report_figures/pt_hedland_data_extent.png}}

  \caption{Data extent for Port Hedland scenario. Offshore data shown in blue 
and onshore data in green.}
  \label{fig:pthedlanddataarea}
\end{figure}


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