The Data menu provides options for bathymetry interpolation as well as accessing online bathymetry data. Being able to view bathymetry underneath the grid helps determine the resolution required in the deep and main channel regions compared to shallow regions, which can often have lower resolutions. The Grid Bathymetry Interpolation and Download Online Bathymetry options are shown in Figure 1 and their use is described below.
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Figure 21 Show the bottom elevation of grid cells.
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Figure 22 Grids with bottom elevation at two cross-sections.
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Figure 23 Interpolate the grid block in I direction.
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Figure 24 Grid with bottom elevation.
Besides the interpolation feature, Grid+ has an extrapolation feature. In this case, some cells in the two head ends of the grid are missing the bottom elevation. To fill in their bottom elevation, select the grid layer in the Control Panel and set the cursor in selection mode. Select a grid block that covers both cells missing bottom elevation and cells having bottom elevation. The grid block will be highlighted by changing the color to red. Then RMC to the grid cells to display options and select the Extend Elevations in I Direction option as shown in Figure 25. The bottom elevation values will be extended to the cells that are missing values. As a result, the bottom elevation for those cells is assigned as shown in Figure 26.
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Figure 25 Extend elevation in I-direction.
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Figure 26 Grid cells after extension bottom elevation.
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After interpolating the bathymetry of the grid cells, Grid+ allows exporting the bathymetry to a scatter data file. To do this, RMC on grid layer, then select Create Scatter Data from Elevation option as shown in Figure 27. It will extract the grid node’s elevation and then create an XYZ scatter layer in the Layer Control. It is named as “XYZ from Grid”. RMC on XYZ from Grid layer, select Export Data Point ( as shown in Figure 28) and browse to the location to save the file, enter a file name, then click OK button to export the layer to a file.
Anchor Figure 27 Figure 27
Figure 27 Create scatter data from elevation.
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Figure 28 Export bottom elevation to data file.
Download Online Bathymetry
After selecting the Download Online Bathymetry option, the Download Online Data form will be displayed as shown in Figure 29. Users are able to select data set using the drop-down Data Set. The currently available open-source sites are:
- GEBCO 2021: This is 2021 GEBCO’s gridded bathymetric data set, the GEBCO_2021 Grid, is a global terrain model for ocean and land, providing elevation data, in meters, on a 15 arc-second interval grid. The data information can be found on GEBCO's website GEBCO 2021.
- GEBCO 2014: This is 2014 GEBCO’s gridded bathymetric data set. The data information can be found on GEBCO's website GEBCO 2014.
- GEBCO 08: a continuous terrain model for ocean and land with a spatial resolution of 30 arc-seconds released by the General Bathymetric Chart of the Oceans (GEBCO) in 2009. Bathymetric data is available to download, and the user manual can be found on the website GEBCO 08.
Depending on the data set selected, different data information is provided in the Spatial Information section. The Data Extraction Limits is auto-set to the whole model domain, but the user can manually select the specific area by checking to Using Polygon File and browser to the closed polygon that contains the area inside.
Click on Download button and Grid+ will download and apply the bathymetry data of the selected Data Set to the specific defined area.
Anchor Figure 29 Figure 29
Figure 29 Download online data for bathymetry.
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