Kathmandu - Now and then with optical images - Urban detection - Continued
|  | Combined RGB image: 2001, 1989, 1976 | |
Expansion of Kathmandu
There are different ways of showing the multitemporal expansion of Kathmandu using the three images produced in the 'Detection of Urban Areas' exercise. A good one is to combine the three images into one RGB image.
Open the three images and choose Image>Combine from RGB... and select the 2001-image for "Red", the 1989-image for "Green" and the 1976-image for "Blue".
Explain the constructed RGB image.
Limit your attention to the very bright (white), the yellowish and the reddish colours within the city limits.
Which optical property (physical principles) produces this specific colouring?
Describe the expansion of Kathmandu between 1976 and 1989, as well as its expansion between 1989 and 2001. During which period did the city grow most?
What is the main direction of the expansion?
What will happen to the airport if Kathmandu expands any further?
Do you know of other cities in the Asian region where the airport had to be rebuilt in a new location due to the expansion of the city?
| | | Measuring the circumference of Kathmandu in 2001 |
Calculating surface change
The images produced in the 'Detection of Urban Areas' exercise will help us calculate the circumference of Kathmandu in the various years, as well as show the resulting surface changes.
The images need to be converted in order to facilitate measurement.
Open the image Kathmandu_2001_1sub4.tif. Convert the image to an image with LUT by choosing Image>Convert to...>Image with LUT. Double click on the lower bar. A pop-up menu opens. Select the button with the vertical line. Double click on the lower right (white) square and change the colour white into a colour of your choice. Modification of the colour is only to make drawing of the measurement polygon easier.
To measure the approximate circumference of Kathmandu in the year 2001 choose Image>Measure tool and change the Units to metres.
Draw a polygon around the city limits and close it by clicking the right mouse button. The single segments, as well as the circumference (area in m²), appear in the 'Measurement tool'.
Repeat the steps for the 1989 and 1976 images, and note the measured areas.
Calculate the growth of Kathmandu between the years 1976 and 1989, as well as between 1989 and 2001 and between 1976 and 2001.
Calculate the percentage of change, and describe the growth during the various time periods.
Based on the three images and your analysis of the urban expansion, discuss the possibilities and constraints of further expansion of the city in the Kathmandu Valley.
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