Delete Bottom Elevation
The Delete Bottom Elevation tool is used to clear the bottom elevation of the nodes within a defined area or in the gridline.
To view the bottom elevation of grid nodes, select the grid layer in the Layer Control, then RMC to display options, and select Show Labels / Bottom Elevation as shown in 2459467777. The bottom elevation values of nodes is then displayed. The following steps describe how to remove the bottom elevation of selected grid nodes.
- Select the grid layer in the Layer Control by LMC on that grid layer
- Set the mouse in the selection mode, hold the Shift key and LMC on two grid nodes either on the same grid line segment or different gridline segments. The grid block will be highlighted. Next, release Shift, then RMC to show options, and select the Delete Bottom Elevation, as shown in 2459467777. As a result, the bottom elevation of nodes will be removed.
- To update the view of the bottom elevation of grid nodes after using the Delete Bottom Elevation, select show labels for bottom elevation as mentioned in 2459467777, the grid nodes whose bottom elevation has been removed will display as NaN labels as shown in 2459467777.
Figure 1 Show bottom elevation labels of grid nodes.
Figure 2 Delete Bottom Elevation option.
Figure 3 Bottom Elevation labels of grid nodes after using the Delete Bottom Elevation option.
Modify Bottom Elevation
The Modify Bottom Elevation option is used to change the bottom elevation values of nodes in the defined area. The steps to define the selected gridline or grid bock are similar to the Delete Bottom Elevation option described above. After defining the impacted area, RMC to display options, and select the Modify Bottom Elevation as shown in 2459467777. The Modify Selection form will display as shown in 2459467777. The radial options of this form are described below.
Assign a Constant Value: Select this option, enter a constant value in the Value field then click the Apply button will assign that value to all nodes within the grid bock. The value displayed in the Average field is the initial averaged value calculated from the nodes within the grid bock.
Add a Value To: Select this option, enter a constant value in the Value field then click the Apply button will add a value to each existing value of nodes within the grid bock.
Subtract a Value From: This option is the opposite to the Add a Value To option.
Multiply with a Value: Select this option, enter a constant value in the Value field then clicking the Apply button will multiply the bottom elevation value of each node within the grid bock with a value.
Divide by a Value: This option is the opposite to the Multiply with a Value option.
Delete Selected Values: This option will remove the bottom elevation values from the selected nodes. It works like the Delete Bottom Elevation option that is described above.
Apply: Click this button to proceed with the radial option.
Close: Click this button to close the form.
Cancel: Click this button to cancel option selection, even clicking the Apply button previouslyWhen building an EFDC model, we need a bottom elevation (or bathymetric data file) assigned to the model grid. However, we just have cross-section files in the model domain. So, how do we create a bottom elevation file for the model grid by using this cross-section?
This page will provide steps to do this.
Grid+ allows us to create a data point file from grid cells that already have the grid's elevation. As a model setting step, we use that file to assign the initial condition to the model grid cells.
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The grid used for generating the bottom elevation file does not have to be the same as your model grid. The density of points in the bottom elevation file will be based on the grid's resolution. |
- Load the cross-sections file, and after that, generate a grid to cover the cross-section, as shown in 2459402261. To show the color ramp of the cross-section, press Alt+C, then set Min. and Max. values.
- Draw a polyline to cover grid cells with cross-section by selecting Add a new polyline button from the toolbar, as shown in 2459402261.
- Press the S key from the keyboard (selection mode), select the overlay layer in Layer Control panel, then click on the polyline, then it will be highlighted, as shown in 2459402261. Right-mouse click and select Interpolate Grid Elevations as shown in 2459402261.
- Next, select the grid layer in the control panel, Right-mouse click on that layer, then select Show Properties/Bottom Elevation, as shown in 2459402261.
- Apply step 3 for grid cells in other cross-sections. We will have cells in two heads of the grid, which have elevation as shown in 2459402261.
- Select entire of the grid by selecting the grid block option, then select Interpolation Elevation in I-Direction as shown in 2459402261. 2459402261 shows the entire grid' elevation color ramp after interpolation.
- Select the Grid layer and Right-mouse click, then choose Create Scatter Data from Elevation as shown in 2459402261. As a result, a new layer, "XYZ from Grid" will be created in the layer control. We can turn off the grid layer and see the data points as shown in 2459402261
- Now we can export the grid's elevation to a data point by selecting "XYZ from Grid" layer and right-mouse click to select Export Data Points as shown in 2459402261. As a default setting, Grid+ will export to a data file with three columns: the first column is longitude, the second column is latitude, and the last column is elevation value. Note that the unit of the elevation value is the same as the unit of the values in the cross-sections. In case we want to export to a data file in the UTM zone coordinates, we can use the feature Convert in Grid+ before exporting.
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Figure 1. Load cross-sections with a generated grid.
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Figure 2. Draw polyline to select grid cells with cross-section.
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Figure 3. Select the interpolate grid elevation option.
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Figure 4 A Modify Bottom Elevation option. A Show bottom elevation of cells.
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Figure 5 Modify Selection form.
Interpolate Bottom Elevation in I- or J-Direction
Sometimes a grid will have nodes that have different values for bottom elevation, and are some nodes are without bottom elevation values (NaN represents missing values) as shown in 2459467777. This option is used to interpolate and fill the bottom elevation in the I direction of the selected nodes. Displaying the I,J indices in advance helps to define which one is I or J direction.5. Bottom elevation of grid cells overlay cross-sections.
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Figure 6 Show bottom elevation labels of a grid6. Modify Selection form.
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7 Bottom elevation labels of a grid after using Interpolate Elevation7. Grid's elevation after interpolating in I-
Direction optiondirection.
Extent Bottom Elevation in I- or J-Direction
This option extents the first or last data points to fill the missing data. For filling missing data between grid points, please use the Interpolation Elevation in I-Direction or in J-Direction.
Create XYZ Data from Block
After defining a grid block, then RMC display options as shown in 2459467777, select Create XYZ Data from block option to create an XYZ layer in the Layer Control. This contains the coordinates and elevation of nodes and displays as points, as shown in 2459467777. To export this layer to an external file, RMC on the layer then select Export Data Points option.
Figure 8 Create XYZ Data from Block option.
Figure 9 Generated XYZ layer
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Figure 8. Grid's elevation after interpolating in I-direction.
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Figure 9. Grid's elevation data points.
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Figure 10. Export Grid's elevation to data file.