Go to the Tools menu to access a tool to make a georeferenced map and general settings, as shown in Tool Menu. The function of each option is described in the table below.
Figure 1 Tools menu options.
| Options | Description |
|---|---|
| Image Georeferencing | This option allows the user to make a background georeferenced map (described in detail below). |
| Settings | General settings for Grid+ |
Image Georeferencing
Suppose that we define a region in Google Earth with two points (P1 and P2), as shown in Tool Menu. We will save the image to a file (with *.jpg extension format).
Go to the Tool menu from Grid+ GUI, select Image Georeference and then the Image GeoReference Tool form appears, click 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 Tool Menu. 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. Click 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).
Figure 2 Make an image file with at least two points from Google Earth.
Figure 3 Add an image to the Image georeference tool.
Now we go to assigning World X and World Y coordinates to defined points. Click the Clear Points to empty the Control Points frame and then using the vertical and horizontal bars as shown in Tool Menu 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 entering 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 entering coordinates for World X and World Y (UTM coordinates). The UTM coordinates of the P1 and P2 have been defined previously, as shown in Tool Menu.
Figure 4 Define and update coordinates for the control points.
Next, click the Save button, the Save As form appears, enter a file name (note that the file name must be the same as the file name of the image). Select extension *.geo for file type then click the Save button (Tool Menu).
Figure 5 Save the georeferenced file.