Start the software application of your choice and open the image on the right (download to your computer first) by clicking “Open Picture" in the File menu.
Use the selections within the menu button below “Satellite Image Visualization” to examine the relative intensities of near infrared (IR), and Red (R) and Green (G) light reflected from the Earth’s surface and displayed in the image on your screen.
Use the selections under the dropdown menu in 'False Color' or 'Data in Images' in the DigitalImageBasics program, or the 'Enhance Colors' tab panel in AnalyzingDigitalImages, to examine the relative intensities of near infrared (IR), and Red (R) and Green (G) light reflected from the Earth's surface and displayed in the image on your screen.
There are 13 Visualizations:
1) Standard color composite of Landsat imagery
2-7) IR, Red, or Green as Color or Gray:
A color or gray shade image of only one set of satellite measured intensities. Gray shades allows unbiased viewing of the intensities, and color illustrates the actual contribution to the color composite being displayed on the screen.
8-10) IR v R, IR v G, or R v G:
Display the difference between two sets of measurements (A v B means Intensity A – B).
11-13) Normalized versions of IR v R, IR v G, or R v G
Select analysis tools from the dropdown menus under 'Data In Images' in DigitalImageBasics or 'Spatial Analysis' in AnalyzingDigitalImages.
Question: What are the maximum and minimum x and y values you can find on the satellite image?
Question: Using the small white square, which represents one mile along each edge, in the lower left of the image, what is the number of pixels that represents 1 mile? Assuming the edge of one pixel touches the edge of the neighboring pixel, what is the size of one pixel? How many pixels represent 10 miles?
Question: This image is oriented so that north is up and east is to the right. The east-to-west and north-to-south extents of the satellite image are how many miles? What is the distance from the upper-left corner to the lower-right corner of the image? Hint: you will need to use the Pythagorean Theorem if you are using the pixel analysis tool or you may use the line length in pixels output from the line analysis tool.
Question: What is the greatest distance across the snow cover observed on Mt. St. Helens in the lower left corner of the satellite image?
Question: What is the greatest width across the lake observed in the left center of the satellite image? What is the greatest length across the lake?
Question: Using the line analysis tool, measure the diameter of caldera formed by the eruption. A caldera is the crater formed by a volcanic explosion or by the collapse of a volcanic cone. Find the location (x,y coordinates) of the center of the caldera and compare this to the location of the center of the volcano as seen in 1973. Does this explain the direction where most of the volcanic ash fell? Combine this measurement with an interesting measurement reported by on the USGS Earthshots web site to estimate how large an area of solid rock was turned into volcanic debris: “Before the eruption, Mount St. Helens towered about a mile above its base, but on 18 May 1980 its top slid away in an avalanche of rock and other debris. When finally measured on 1 July 1980, the mountain’s height had been reduced by 1,313 feet— from 9,677 feet to 8,364 feet.” From Foxworthy and Hill, 1982, p. 11. Lipman, Peter, W., and Mullineaux, Donald, R., (ed.), 1981, The 1980 Eruptions of Mount St. Helens: Washington, U. S. Geological Survey Professional Paper 1250, Washington, D. C. (844 p.), p. 134.
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