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In this exercise we will look at the urban growth that occurred in Córdoba over 37 years, from 1972 to 2009. To do so, we will use three Landsat images of the area taken in various years:

- Landsat MSS of 25/02/1972
- Landsat TM of 17/01/1992
- Landsat TM of 16/02/2009
 
We will first compare the images visually.

Download and install the LEOWorks Image Processing Software from the right menu.

Download the Cordoba.zip file from the right menu and put it in a folder on your hard disk. Unzip it.

The Cordoba folder contains all the data you need for the exercises. The satellite images are prepared as single band images (e.g. 2009_cordoba_B1 is band1 of the 2009 image, etc).  
 
a) Colour composites
 
Start LEOWorks.

For LEOWorks4: Open/Multiple Files as Single Dataset: 2009_cordoba_B1.tif to 2009_cordoba_B7.tif, calling the merged image ‘2009_cordoba’.

For LEOWorks3: Open: 2009_cordoba_B1.tif
>In Image Preview window click OK.
>Display band1
>Now repeat the process for the other 2009 bands.

The image is rather dark and the contrast is too low. We are therefore going to enhance the image. A greyscale image consists of 256 grey levels, from black (0) to white (255). However, not every grey level is used in this image. Inspect the histogram.

If we expand the number of grey levels used, contrasts in the image will be more visible. Features such as city boundaries will be more apparent.

Go to Interactive Stretching. This opens a window which displays the histogram of the image to the left. In order to enhance the image, use the sliders so that the Output histogram/Displayed Histogram to the right fills the entire window with values from 0 to 255.

After you’ve done this, click Apply.
 
 

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