During making a grid for water bodies, viewing the bathymetry underneath the gird is meaningful as it gives an idea about the high resolution of cells in the deep and main channel regions and the low resolution of cells in shallow regions. The Data menu supports do this. It includes Grid Bathymetry Interpolation and Download Online Bathymetry as shown in Figure 1. The function of each option is described in the table below.
Figure 1 Data menu options.
Grid Bathymetry Interpolation
Suppose that we have a cross-section file (filename XS.ldb), the file contains cross-sections. Each cross-section has the following information (Figure 2).
- The first row is the name of the cross-section
- The second row has a number of data points (e.g 111), and a number of columns (e.g 3) of each data point. It includes coordinates (X, Y) and Z (elevation)
- Data points start from the third row to end
Figure 2 Cross-section data format.
From the Import button in the main toolbar, select Import Cross-Sections option, as shown in Figure 3. Then the Import Cross-Sections form appears, browse to the cross-section file then click the Open button (Figure 4), as the result, cross-sections are displayed as shown in Figure 5.
Figure 3 Import cross-sections option.
Figure 4 Import cross-section file.
Figure 5 Cross-sections loaded.
To display the elevation of the cross-sections by color ramp, press Alt+C from the keyboard, and the Specify Elevation will pop up, and enter Min and Max values for elevation range (this range is based on the Z column value in the cross-section file). In this case, enter 110, 120 (Figure 6). Then click OK button, the cross-section will be displayed as shown in Figure 7.
Figure 6 Cross-sections loaded.
Figure 7 Cross-sections displayed in color ramp.
After loading the cross-sections, now we are going to interpolate bathymetry for the grid. Selecting the grid layer in the Layer Control panel, next select Grid Bathymetry Interpolation option from the Data menu as shown in Figure 8. The Topographic Interpolation form will be displayed as shown in Figure 9.
Grid Layer: That is the name of the selected grid layer that we are going to interpolate its bathymetry.
Using Visible Data: That is the number of data points. In this case, there are 2234 points from the cross-section file.
Interpolation Options: There are two options including Update Missing Only (update elevation values for the missing grid nodes only, in case other nodes already have elevation values) and Overwrite All Data (create new elevation values for all grid nodes and overwrite the nodes that have existing elevation values).
Interpolation Method: The Grid+ is using one interpolation method currently. It is Inverse Distance Weighting (IDW). The IDW Options frame allows changing its properties.
Clicking the Interpolate button to start interpolation. Then click the OK button to close the form.
Figure 8 Grid Bathymetry Interpolation.
Figure 9 Topographic Interpolation form.
Figure 9 Topographic Interpolation form.
Figure 9 Topographic Interpolation form.
Figure 9 Topographic Interpolation form.
Figure 9 Topographic Interpolation form.
Figure 9 Topographic Interpolation form.