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Exercise 3 - Annapurna I Region - Continued 
Open the following three images in LEOWorks:
Look at the false colour image.
Which colour represents the areas covered by ice and snow?
What about bare rock and vegetation? Compare this with the 3-2-1 combination opened before.
Ice and snow can be identified easily by its colour, which is somewhere between magenta and violet. Bare rock shows up in green and vegetation in a red-green tone. Let's now concentrate on the main glaciers visible in the image, which flow from the mountain massif in a Southwest direction.
What is the extent of the glacier, and where does the moraine begin?
Although the structure on the floor of the valley looks very similar to what we would expect from a glacier, the false-colour image tells us something different - there is no ice in that area! We find two shorter tongues of ice entering the valley from the North and from the West, respectively, but they end with relatively sharp edges. Let's now measure the length of the moraine using the Image>Measure Tool of LEOWorks.
How much of the original length of the glacier remains?
What is the typical form of the cross section of the valley formerly filled by a glacier? What consequences could the shrinking of glaciers have for the viability of the terrain, and for tourism? We have already seen that the 4-5-2 band combination does not show vegetation very well, and neither does the 3-2-1 band combination, especially in this alpine environment with relatively sparse vegetation. We will therefore compare two different methods - the first is the 4-3-2 band combination, and the second will be the Normalized Difference Vegetation Index (NDVI). Open the image anapurna_landsat_2000_Top_band_432.tif in LEOWorks. Select a few of the transition zones between glaciers and bare areas in this image using the 4-5-2 band combination.
In which band combination is it easier to separate ice and snow from rocks?
In the next step, identify areas of vegetation. Keep in mind that they show up in red in the 4-3-2 band combination.
Where in the image do we find vegetation? Compare this with the 4-5-2 band combination. Where is it easier to identify vegetation? Look at the 4-3-2 band combination. Can you separate different classes of vegetation intensity? What is their relation to the altitude? We will now assess vegetation intensity using the NDVI. Open the following images in LEOWorks: anapurna_landsat_2000_Top_band_4.tif and anapurna_landsat_2000_Top_band_3.tif Let's select Image>Arithmetic. In the dialogue that now opens, select band 4 as first image, band 3 as second image, and NDVI as the calculation method.
What does the resulting image look like?
Obviously we have to enhance the image to be able to see something. We do this using Enhance>Interactive Stretching and shift the colour bars from the left and right side of the histogram towards the centre, until the darkest parts are black and the brightest are white.
Which parts of the images are brightest? Compare this with the 4-3-2 band combination.
Bright grey and white show vegetation. Where can we find it?
What will happen to the vegetation, if the glaciers continue to shrink?
Last update: 16 April 2013
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