Geoscience Reference
In-Depth Information
Modelling LAT relative to a geoid is realized by referencing the hydrodynamic
model to the chosen geoid. (Slobbe et al.
2012
). Terrain Irregular Network (TIN)
and Digital Elevation Model (DEM) are needed to view the 3D model of seabed
profile. The set of constituents used to derive the observed LAT values is that set
for which the root means square (RMS) of the differences between the observe
water levels and the reconstructed astronomical tide is lowest. The tidal lines can
be derived from the integration of various datasets as follows:
• Topography data
• Bathymetry data (multi-beam sonar)
• Seabed topography data
• Tide data
• Light Detection and Ranging (LIDAR)
• High Resolution Satellite Image.
There are two methods in creating tidal model. The first method is by inter-
polating the tide height between tide gauges. This method only works well along
open coastlines. It suffers major limitations in complex foreshore like bays, islands
and rivers. So in this case, the second method is introduced. This method is
localized a hydrodynamic model. Hydrodynamic model represent the movement
of water and solving governing equations for oceanic movement. This hydrody-
namic model has been derived using bathymetry data to get the depth and ocean
tidal constants observed by tide gauges as the boundary conditions. The examples
of global tidal model are FES2004, GOT4.8 and ORI96. The final data or result of
tidal model contains the constituents and the constituents will separate by phase
and amplitude. The amplitude and phase contain the longitude, latitude and the
value of the respective constituents. Figures
5
and
6
show the phase and amplitude
of the S2 constituent from the model Ori96.
5 Delineating the Littoral Zone
Quadros and Collier (
2008a
) summarized the steps to delineate the littoral zone.
The littoral zone contains a number of tidal lines. A tidal line is used to describe
the Intersection between a specified tidal datum and foreshore terrain. The step of
delineating the zone is by computing the line of HAT and LAT using both
bathymetric and topographic DEMs. The HAT line is derived from bathymetric
data and the line of LAT is derived from bathymetric data and tidal lines. Figure
7
shows that the shoreline was present by many of sources and the data have been
overlay. The different of grid of the data, so the two line of data have been
analyzed for the intersection of the data. It is the digitizing data from Spot5
satellite image and bathymetric data. Figure
8
shows the zero elevation from line
