To make a georeferenced map or access general settings for Grid+, go to the Tools menu as shown in 2128019457During 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.
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Figure 1 Tools Data menu options.
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This option allows the user to make a background georeferenced map (described in detail below).
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General settings for Grid+
Image Georeferencing
Although Grid+ has online maps, sometimes a user may want to use a proprietary background map they possess or use Grid+ offline. In that case, a georeferenced background map can be created as described here.
Define the region of interest in Google Earth with two points (P1 and P2), as shown in 2128019457. We will save the image to a file (with *.jpg extension format).
Go to the Tools menu from Grid+ GUI, select Image Georeference and the Image GeoReference Tool form appears, click the Add Images button and browse to the image, which was generated by Google Earth.
By default, the coordinates of the four corner points of the image are updated in the Control Points frame, as shown in 2128019457. LMC on the row numbering from the table to select a point of the Control Points, then we can find that point by clicking the Find Point button, or remove that point by clicking the Delete Point button. Clicking the Clear Point button will delete all points in the table. Click Add Point button then LMC on a point in the image to add a new point to the table (a new row is added).
Grid Bathymetry Interpolation
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Figure 2 Make an image file with at least two points from Google Earth.
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Figure 3 Add an image to the Image georeference tool.
Now we will assign World X and World Y coordinates to defined points. Click the Clear Points to empty the Control Points frame and then usie the vertical and horizontal bars as shown in 2128019457 to move the image to find the defined points (P1 and P2).
- Assigning coordinates for P1: After finding the P1 on the image, LMC on that point, its Image X and Image Y are updated in the Control Points frame. Now enter the coordinates for World X and World Y (UTM coordinates) then press the Enter key, and it will jump to the second row.
- Assigning coordinates for P2: Finding the P2 on the image, then LMC on that point, its Image X and Image Y are updated in the Control Points frame. Now enter the coordinates for World X and World Y (UTM coordinates). The UTM coordinates of the P1 and P2 have been defined previously, as shown in 2128019457.
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Figure 4 Define and update coordinates for the control points.
Next, click the Save button, the Save As form will be displayed. Enter a file name. Select extension *.geo for file type then click the Save button (2128019457).
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Figure 5 Save the georeferenced file.
The georeferenced map can be made from multiple images by using the Add Images button and then assigning coordinates as described above. In case we want to remove the image from the Image Files frame, select that image then RMC to display the options. Select Remove Selected Image as shown in 2128019457. Selecting Remove All Images will delete all images in the Image Files frame.
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Figure 6 RMC options in the Image Files frame.
Settings
Selecting the Settings from the Tools menu will show the Global Settings form as shown in 2128019457. The values in this form are the default settings.
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Figure 7 Grid+ general settings.