Role of the Geographical Sciences: The perspectives and tools of the geographical sciences used by geographers, geologists, ecologists, and others provide insights into soil erosion, flood magnitude and frequency, and ecological adjustments to climate change on both contemporary and paleotimescales. (NRC 2010, p. 22)
Let’s investigate the Aral Sea region using the ArcGIS online Aral Sea land use slide presentation. There are a short series of activities to learn how to use the image analysis software, ImageJ. This software is fun to use and what you learn in this investigation can be used on any series of images, even photos you take of a person! The lesson concludes with an investigation of how the size of the Aral Sea is changing in the first decade of the 21st century. All imagery is embedded on the website needing no exterior navigation.
These resources serve as an introduction to the area of the Aral Sea and the issues causing its environmental demise. Use the link below to familiarize yourself with the region. Click through the slides to understand the region better. To see the presentation slides as intended, view the larger map version. Click the link under the map here.
Instructions: When the page opens you will see a set of tools that allow you to ask important questions of imagery. Answer the questions on your Student Answer Sheet. First you will play with and get the feel for the interface.
The tool bar looks like this:
Pictures and Color
1. How pictures keep track of color:
a. Move your cursor around the picture. What changes directly underneath the tool bar as you move your cursor?
b. Can you find where a picture considers its origin? (Where the x and y values are 0,0?)
c. What are the coordinates of the opposite corner?
d. What do the largest coordinate numbers mean in terms of picture resolution?
e. Just after the coordinate information is a value number. This tells you how bright the red, green and blue light should be for this pixel. Now move your cursor over the picture until you get to the darkest part of the Aral Sea you can find. What values do darker pixels have?
f. Move your cursor to the white clouds in the upper left of your picture. What values represent white in pictures?
Moving in and out of areas of interest in a picture:
2. Zooming in or out of the picture can be done one of several ways.
a. Choose the zoom tool and left click to zoom in.
What is the maximum percent zoom to which you can magnify a picture? (Click repeatedly and look in the top of picture window.)
b. Right click with the zoom tool and it allows you to zoom out.
What is the maximum outward zoom that ImageJ allows? (You may have to resize your picture view box to see the percent.)
c. Hold your shift key then click (right or left) back to a middle level zoom of your whole picture.
d. Click while holding the shift to drag a box. This allows you to zoom to the area you have drawn. Zoom to the white area in the top left of the picture. What are these white features: sand, snow, or clouds? How did you conclude this?
3. Panning. (While still zoomed in to the top of the picture)
a. Click and drag the northern part of the Aral Sea to the center of view. Pan around the outskirts of the water. Where does the northern river, Syr, empty into the Aral Sea?
b. Depressing the space bar and left clicking the image will also allow you to pan regardless of what tool button is clicked. Where does the southern Amu enter the Aral Sea?
4. Moving through the years in this stack of pictures.
a. This picture was taken by satellite in 2000. Click once on the picture of the Aral Sea and grab the slider bar at the bottom of the picture view box to slide it to the right. What is happening to the picture?
b. Use the scroll wheel on your mouse to flip back and forth through the years. Each picture is roughly one year later than the picture before it. Can you figure out what year the Aral Sea’s level was the lowest?
Setting the scale of a picture so you can measure features in the picture.
5. Right now, the images are not aware of pixel size; therefore you will need to give it that information. You can do that by finding a known feature on the image in a virtual globe that has a scale bar and then input that scale onto your image.
a. You will set the scale for the image based on the length of the island that existed in the middle of the now separate parts of the Aral Sea.
b. Zoom in to the area highlighted with a yellow box in the image using your shift -zoom tool.
c. Use the line tool to click and drag a line from the upper west of the image to the point on the east of the triangle shaped ex-island.
d. This island is 14.00 miles (as measured on a virtual globe). You will use this information to set the scale. Make sure to change the Known Distance box with the number “14” and click the box in front of Global to apply this scale to all the images in the stack.
e. Click OK and you are now ready to measure other distances with the line tool. What is the length of the original Aral Sea?
f. Drag a line through the north south length of each segment of the Aral Sea and choose Analyze > Measure to find these lengths.
g. Right click the line tool to change to segmented line then roughly measure the outer shoreline of just the southern Aral Sea. (Remember to click on Analyze and Measure to store your answer) What is the approximate outer perimeter of the combined Aral Sea segments?
6. Use the wand tool to find like areas and measure them.
a. Double click the wand tool. Double clicking any tool opens up the tool’s preference settings. We will give the wand tools some leeway in finding pixels of like color for the Aral Sea
b. Set the tolerance to 12
c. Click on each Aral Sea segmented areas with the tool to select all the pixels that look like the Aral Sea.
d. Hold the shift key down and click on other parts of each segment until you’ve highlighted as much of the sea as you can.
(This may take some practice because if the Shift key isn’t depressed all the way you can lose your selections.)
Hint: Hover over areas you know to be joined but show they are separate until the arrow becomes a plus. This means it is hovering over an area not yet selected. Continue holding down the shift key and click so that ImageJ conglomerates your choices. See images below for example of where to click to conglomerate your choices.
e. When the whole Aral Sea has been highlighted, click Analyze in the top pull down menu and choose Measure.
f. A popup window will appear showing information about the area, perimeter and other measurements. You can measure many other things but area and perimeter is all we need for the current exercise. How far off were your perimeter measurements from the computer determined ones? (In percent)
7. Track the progress of the loss of water in the Aral Sea over the past decade.
a. Use either the slider at the bottom of the picture or the scroll wheel on your mouse to advance to the next year’s (2001) image in the stack. The year is encoded in the file name to make sure you haven’t skipped a year. It also is stated by which slice you are measuring in the Results window.
b. Use the wand tool you used in the steps above to highlight the area of the Aral Sea.
c. Click the Analyze > Measure pull down menus and measure the area of the Aral Sea for this year.
d. The area for this year will now be in the results window along with the previous years
e. Advance to the next image and determine the Aral Sea's areas until you have found the area for all 3 of the Aral Sea images. Make sure to only measure each slice once.
Make a graph of the Aral Sea area loss using Excel or another spreadsheet program.
8. Highlight your ten years of values from the results window and click Edit > Copy
9. Open the spreadsheet and paste your values into the first cell (1A)
10. Right click the left column box “1” and insert a new row.
11. Label the columns headings: Year, Area_SqMi, Perimeter_Mi, and Slice
12. Highlight the first two columns of data (Year and Area)
13. Click the Insert tab and choose the Scatter plot with straight lines and a quick graph will appear.
14. If it hasn’t already changed, click on the design tab and choose to view all chart layouts.
15. Choose the Chart layout that gives the trend line (line of best fit) as shown. Change the x and y axis with appropriate titles and clean up the chart to communicate your results.
a. How many square miles of Aral Sea surface are lost yearly? (Obtainable from the trend line formula)
b. If this trend continues, when would you predict the Aral Sea to dry up?
c. Do you think this will happen? Give reasons to support your choice.
d. How are we changing the physical environment of Earth’s Surface?
“The approaches and techniques of the geographical sciences can help identify and quantify the biophysical changes unfolding on Earth’s surface, and they can offer insights into the processes shaping those changes at different scales. Geographical science approaches and techniques thus have an important role to play in advancing scientific understanding of biophysical changes and facilitating the efforts of resource managers and policy makers to confront Earth’s changing environment. “ (UCP, 29)