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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Draw a polygon to cover the grid cells near the cross-sections as shown in Figure 18. Then, change the cursor to select object mode (press the S key or select the Select Object in the main toolbar). Select the overlay layer (the layer that contains the new polygon), then LMC on the polygon (it will be highlighted by changing color to red), then RMC to display options, and select the Interpolate Grid Elevations option as shown in Figure 19. A message will be shown as in Figure 20 when the interpolation process is complete. Click the OK button to close the message.
RMC on the grid layer and select Show Properties / Bottom Elevation to display the bottom elevation of the grid after its grid nodes are assigned elevation values, as shown in Figure 21. Do similar steps to interpolate the bottom elevation of grid cells near the second cross-section. Figure 22 shows the grids with bottom elevation at two cross-sections. Based on the grid elevation in two heads, we will interpolate the entire grid.
Then, select the grid layer in the control panel and change the cursor to selection mode. Select the upper grid node of the interpolated cell and hold the Shift key to select the second node of the other lower interpolated grid cell, the selected grid block should fully cover 2 regions of the newly interpolated grid cells ( the grid block will be highlighted by changing the color to red) then RMC to display options, and select the Interpolate Elevations in I Direction option as shown in Figure 23. Figure 24 presents the grid bottom elevation after interpolation.
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Figure 16 Cross-sections loaded and located in the river segment.
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Figure 17 High-resolution grid covers the cross-sections.
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Figure 18 Draw two polygons covering grid cells and cross-section.
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Figure 19 Interpolate grid cells near the cross-section.
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Figure 20 Grid Bathymetry Interpolation message.
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Figure 21 Show the grid bottom elevation.
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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 interpolation, Grid+ has a feature to replicate the grid elevation. For example, in this case, some upper grid cells are missing the data of bottom elevation. Firstly, select the grid layer in the control panel and change the cursor to selection mode. Select a grid node and hold the Shift key to select the second node, the grid block will be highlighted by changing the color to red. Note that the number of grid cells having bottom elevation values should be similar to the cells missing data. 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 expanded to the upper cells. Figure 26 presents the grid bottom elevation after extension.
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Figure 25 Extend elevation in I-direction.
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Figure 26 Grid cells after extension bottom elevation.
Download Online Bathymetry
After selecting the Download Online Bathymetry option, the Download Online Data form will be displayed as shown in 2127790207 Figure 27. 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.
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Figure 15 27 Download online data for bathymetry.
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