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In the pop-up Import Over Layer window, go to the directory where the overlay file is saved the select and open the Shoreline.p2d file. Before the shoreline is displayed, indicating the coordinate system is required. For the New York Harbor, the coordinate system, or projection, is UTM Zone 18 in the Northern Hemisphere (Figure 2).
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Figure 2. Loading overlay file.
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Grid+1.0 shows the imported shoreline as in Figure 3. To check is the shoreline overlays the correct area in the background map, turn on the background map by clicking the lightbulb icon on its layer.
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In the main toolbar, LMC the Add a new spline button to activate the drawing mode (Figure 5). The user can also RMC on any layer and select Create New Spline Layer.
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Draw the splines along the river banks (line 1 and 2 in Figure 6) and make the first grid section by adding lines 3 and 4. The splines must intersect so that a grid is generatable. Next, set the cursor to selection mode by clicking the Select object button, or us the shortcut key S.
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To create a grid based on the constructed splines, select the splines layer then click the Create grid from splines button in the main toolbar. In the pop-up Create Grid from Splines window, give the dimension properties of the grid, including the grid points in I and J direction. Click Ok and the resulting grid is shown (Figure 9).
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Figure 8. Creating grids.
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Repeat steps 2-4 to build neighboring grids. The subsequent grids must overlay the previous ones so they can be merged at the later stage (Figure 11). Also, save the new splines.
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Figure 11. Building neighboring grids.
Figure 12 shows how to merge grids. First, select the first grid, then click the Select object option and LMC on the first note of the intersection border. Next, hold the Shift key and LMC on the second node of the intersection border, and click the Merge two grids button. Grid+ will create merged grids and place them in a separate layer (Figure 13)).
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To expand the branch grid, the final local cell in Figure 16 must be refined so that there are at least 2 cells that go along the branch in the I/J direction.
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Follow the steps described in Figure 17 to refine the branch channel.
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Next, generate a grid block sized 30x6, as shown in Figure 20. As large spline blocks may cause uneven distribution of grids, the user can make grids from smaller, separated spline rectangles, or create multiple intersecting spline blocks by adding single splines in the middle of a large block.
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Create the grid06_3 from the junction with steps illustrated in Figure 22.
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The identification of I, J indices is required for the determination of the dimension of the subsequent grid block. Click on the first and the last nodes of the branch to define the number of cells along the main river branch. Delete the cells inside the splines as indicated in Figure 24.
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Generate a grid block of 115x8 cells, then connect them to grid06_4 and save the new grids as grid06_5 (Figure 25).
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The complete grids for the New York Harbor is shown in Figure 27.
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To implement global orthogonalization, select the grid layer then click the Orthogonalize grid button in the main toolbar (Figure 28).
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