Part 3—Analyze and Annotate Change
Step 1 – Identify and Highlight Area of Newest Land
- Zoom in on the island whose center is near x=250, y=330. Move between the images to see how the area of the island increased through time.
- Click the magnifying glass on the toolbar and place your cursor on the image. Read the x,y location of the cursor in the Status Bar, just below the tools. X increases as you move to the right and y increases as you move downward. Move your cursor over the island centered at x=250, y=330. When your cursor is on the island, click two or three times to zoom in.
- Use the animation controls to move between the images.
- On the final image, use the freehand selection tool to outline land that appears only in the last imageland that was created between 1992 and 1995.
- Click on the Freehand selection tool on the toolbar.
- Try out the Freehand selection tool by drawing some simple shapes on any one of the images. Notice that you must keep the mouse button down until you are done with the entire shape, and that the selection will automatically close as soon as you release the button. Just click again on the image any time you want to start a new selection.
- When you are comfortable with using the freehand selection tool, go to the third image slice, then click and drag your cursor around the area of the newest land.
- Use as many attempts as you need to get a fairly accurate outline.
- Once the area is outlined, double-click the Eyedropper tool to open the Colors palette and select a bright color to mark the area. Click on the stack of images again, and choose Edit > Fill to fill the outlined area on all three slices of the stack. You will be asked if you want to Process Stack?. Click Yes. Note: If your selection has disappeared, restore it by selecting Edit > Selection > Restore Selection.
- Double-click the Eyedropper in the toolbar then click on a bright color in the palette.
The eyedropper or "color picker" in the toolbar always shows the current fill color.
- Click the image stack again to activate it and choose Edit > Fill to color the area inside your selection line.
- A dialog box will display asking you if you want to Process Stack, click Yes, so that all three slices of the stack with be marked with the fill color.
Step 2 – Identify and Highlight Land Created Between 1988 and 1992
- Move between the first and second images to identify land that appears in the second image but not the first.
- Double-click the Eyedropper tool to select another bright color, then use the Freehand selection tool to outline the land. Choose Edit > Fill to fill the area on all three slices, then save your stack.
- Double-click the Eyedropper tool and select a second bright color for marking the image.
- Click the Freehand selection tool on the toolbar.
- Move between the first and second images of the stack to identify land that appears in the second image but not in the first.
- Click and drag your cursor to outline the land. Use as many attempts as you need to get a fairly accurate outline. Note: it may be easiest to do your drawing on the first image or slice.
- Choose Edit > Fill to color the area inside your selection line. In the dialog box that appears, click Yes so that all three slices of the stack will be marked with the fill color.
- Choose File > Save As to save your work with a new name. Store the image stack in an appropriate location.
Step 3 – Create a Key to the Colors You Used on Your Map
- Return to the unzoomed view by double-clicking the magnifying glass in the toolbar.
- Double-click the Eyedropper tool to open the Colors palette and select white for your active color.
- Use the Rectangular selection tool and Edit > Fill to make a white space in the lower left corner of the image stack. Inside the white space, make small squares of the two colors you used to mark the land in step 2.
- Double-click the Eyedropper tool and choose white from the Colors palette.
- Click the Rectangular selection tool in the toolbar, then drag a rectangle approx. 4 cm by 2 cm (2 inches by 1 inch) in the lower-left corner of the image.
- Choose Edit > Fill to create the white area for your legend. Click Yes to make the space on all three slices.
- Double-click the Eyedropper tool again, then click the color you used to mark the land that was formed between 1988 and 1992 (the second color you used).
- Use the Rectangular selection tool to make a small square (approx. 1/2 cm or 1/4 inch) near the top left of the white space, then choose Edit > Fill. Click Yes in the dialog box that appears.
- Double-click the Eyedropper tool, and click the color you used to mark the land that was formed between 1992 and 1995 (your first color).
- Make another small square below the first one, then choose Edit > Fill. Click Yes in the dialog box that displays.
- Use the "A" Text tool to label each color box to show the range of years the land was created.
- Choose File > New, then click OK to create a new window.
- Double-click the Eyedropper tool and choose the color black for your text labels.
- Double-click the Text tool (the "A") to open the font dialog box. Select the smallest font size and a simple style for your text.
- Click on the blank image window. You'll see the following message: Type, then ctrl+alt+b. Type a sample message there, using Return to start a new line. When the text reads as you'd like it, hold down the "Ctl" key, the "alt" key, and a "b" on your keyboard.
- A dialog box will display asking if you want to Add to Overlay. Click OK.
- Practice adding text to the image several times. When you feel comfortable with the text tool, close the practice image and return to the time-series stack.
- With the Text tool selected on the tool bar, click near the top color square in your legend area on the image.
- Type a descriptive label such as "Land created between 1985 and 1992." Use a carriage return within the text wherever you want to start a new line.
- You may need to try several combinations of font, size, and line break placements before the text looks pleasing and fits in the white area. You can start the labeling process over at any time by clicking outside of the current text box, then click again to start over. You can also move the text box; click and drag it to position it when your text is complete. The arrow keys on your keyboard can also be used to position the text box.
- When you are satisfied with the text, press the "ctrl" key, the "alt" key, and the letter "b" on your keyboard to make the label a part of the image. Accept the defaults in the dialog box and click OK to add it to the overlay.
- If you are dissatisfied with the result, immediately choose Edit > Undo and begin the labeling process again.
- With the text tool still selected in the tool bar, click near the second color square to insert its label.
- Type another descriptive label such as "Land created between 1992 and 1995."
- When you are satisfied with the text, hold down the "ctrl" key, the "alt" key and the letter "b" on your keyboard.
Step 4 – Annotate Other Areas of Change in the Region
Examine the rest of the image stack to identify other areas of change that are visible in the three different slices. At least two other locations show evidence of land reclamation. Use the techniques from this chapter to annotate these areas.
Step 5 – Save Your Map and Write an Interpretative Description to Accompany It
Save or print any one of the three images from your stack. Consider one or more of the questions below, then gather information on the topic(s) and write your interpretation.
- How might dredging affect marine environments where the sediments are gathered?
- Is land formed by dredging just as good as natural land? Why or why not?
- How might land reclamation projects contribute to flooding?
- What legal issues might arise from creating new land? (Should anyone, anywhere, be allowed to create their own land by dredging?)
- Are dredging or land reclamation projects performed in your region? (Several U.S. harbors actively employ dredgers)
- What long-term effects might dredging and land reclamation have on harbor areas?
- Has new land been created in the Pearl River area since the 1995 image? How might you find out?